This could be the problem. I know the Admin on one of the forums had to fix something when a few of us members were all having issues posting on the forum via Tapatalk. I do not know what he did but it did resolve our problem. If Tapatalk works fine on one forum and not the other, then the problem is with that forum and not Tapatalk. I would contact the Admin of that forum and let him/her know that Tapatalk is working properly with the forum for you. It could just be a plug in issue that needs to be corrected. If the problem started after an update, this is most likely the cause.... Hope you get it fixed soon.