From my own exp, it seems that WN will go thru their pic and gif database from time to time and remove any doubles.
If the pic/gif you posted happens to be the double that got removed, than it won't load.
Had this happen to a few of my own posts.
Yes, Neigh007 is correct.
Once your account has any purchase on it, you permanently lose the ability to unlock chapters by watching ads.
This has caught out a lot of people and is a regular topic to show up here.
Wait, Google Translate was working again?
For a long time Google Translate wasn't working since WN implemented a text scrambling 'feature' to stop people from copying novels. I was unaware that any sort of fix had come out. (Other than taking a 'long-screenshot' of the novel to use in Google Translate.)
BloodRaven, is it just the one novel like Vandalieu1234, or is it happening on multiple novels?
It sounds like a tech issue on the WN side of things. In which case, they will need to know which novels are having the problem. And you will have to wait for the WN IT staff to get back to you. (Can take a wile.)
In the meantime, the more info you give, the more others can help, and the faster that WN IT staff can find and fix the problem.
P.S. Due to actions I've seen taken on other posts/sites I feel I need to point out that when I say "more info", I'm talking about things like what platform you're using and what novel you're having problems with. DO NOT give out personal details like phone number, email, home address, etc...
And yes, I've seen people do this when asked for "more info". 
Daoist402831
As far as I'm aware, you lose the ability to watch ads to unlock chapters when you spend money on Webnovel. Like when you buy coins for example.
If you haven't bought anything from WN, then it might be a tech glitch.
If you have bought Coins or anything else on your WN account, then as far as I know you will never be able to unlock chapters by watching ads again.
Of course it's always possible that WN has changed how things work without any notice, again. Something they do all the time.
lealkill
I fully agree and have noticed all of this myself. All of the problems tho, fail to out-weigh just how much easier it is to read the text on a large monitor instead of a small phone screen. Especially if, like me, you are getting on in years and you eyesight isn't as good as it used to be.
dimplz1987
Not haveing the same issue, but, a week or so back I had an Add that didn't bring up any way to exit it at all when it finished playing.
Had to close the App and restart it so I could watch a different Add.
Time consuming, but might help you till WN (or the add providers) IT staff can get the bugs out.
Ella_Sheridan
As others have noted, FPs expire after a set time.
However, there are also different types of FP.
You can only use FP that are compatible with the chapter you are trying to unlock.
Site-wide FP = Works on any chapter
Novel FP = Works on any novel chapter
Comic FP = works on any comic chapter
Genre FP = works on any chapter that matches the 'Genre Tag'. ie. 'Romance', 'Sci-fi', etc.
Specific-Works FP = will only work on the novel or comic that is named in it's description.
The problem is that most the time when you see a total of how many FP you have, it gives you a total of ALL FP, regardless of if you can use them or not.
The only exception is in the app at the point in a chapter when it prompts you to spend your FP to unlock that chapter. This shows the number of 'usable' FP for that chapter.
Dwarkin
Chapter size is the main factor in pricing a chapter, but not the only one as far as I can tell.
As for what the other factors are, I have no idea.
As for how many FP are used to unlock a chapter, that is directly down to coin cost to unlock that chapter.
Up to 14 coins is 1 FP, then +1 FP for every 10 coins thereafter. (15 = 2FP, 35 = 4FP, etc)
Unfortunately, as the coin cost isn't just the size of the chapter, the price of a chapter in one novel can't be used to judge the chapter price in another novel.
This is just what I have observed myself and is not official.
(Other than the coin to FP stuff. That is taken from an official email to another poster on this forum.)
The App is only for Android and iOS systems. (i.e. Apple and Android phones and tablets.)
To use the App on a PC or Laptop you will need to run a phone emulator like 'Bluestacks'.
Seams to have stopped now. Will post again if it starts up again.
Doug_Little
I hear you. It used to be that 1 FP would unlock 1 chapter regardless of size. Now, up to 14 coins = 1FP, 15 coins and every 10 coins thereafter (15,25,35,etc) is +1FP. For example: 25 coins = 3FP. It's just not good enough. Plus the fact that 'Sitewide' FPs are getting very rare now. Most the FPs I get now are 'Genre' FPs.
Just letting you guys at WN know that my anti-virus keeps blocking 'URL : Phishing' infections from your site. It is only being triggered on the WN site and nowhere else so I would think its either at your end or whatever domain(s)/ISP you go though.
vincentatd
This problem only shows up when you reach chapter 38 - 40 of a novel.
In other words, right when you need to start unlocking chapters.
At this point you get a message that roughly says 'This is the end of part one. please download the app to read more.'.
I'm a long time reader myself and didn't notice this had been implemented till one of the authors I follow started a new novel.
It doesn't mater what browser you use.
The only novels that don't have this happen are the 'Fan-Fic' category because you don't have to unlock them.
Paul_2592
There is a workaround, though you still need to get the App to use it.
You just need to use the App to unlock a chapter or 2 for that novel/comic.
You can then read and unlock chapters as normal on PC.
Not ideal, but better than nothing.
Just remember to login to the same account you use on PC.
Keith_Meyer
Once in a chapter that you are reading, tap on the text.
A menu should pop up.
Under the 'General' tab, if you scroll down, you will see the option to turn 'auto-unlock' on/off.
Just remember that it will sometimes turn itself back on when the app updates.