I appreciate the effort that authors, translators, editors & Webnovel staff put into releasing these novels for us. 
So normally I don't mind watching ads or paying SS, but...WHY are the chapters that I previously read, rated & commented on, ADLOCKED? 
Someone, please explain this to me. 
Adlocked?!
I would want to know but I guess they just basically locked everything. That way they can earn money from the ads if you wan to go back to that certain chapters.
I have more than 200 chapters in one series that was locked that I have previously read before.
zhan2ruai If it was just adlocked, you probably never watched ad or unlocked it with SS before. That's the case for me too but because sometimes I accumulate chapters first before reading so those accumulated were not adlocked that time. From what I remember, it was only the latest two chapters adlocked so I never really unlocked the others. :)
a month later
After some investigating, it turned out to be an update issue. All chapters that have not been published or not premium but are "bonus chapters" for multi-release events are ad-locked. The thing is it ad-locked chapters automatically even if you had read, commented, voted or used SS on them because they were "bonus chapters". In the end, I just carried on reading the novels despite this issue.