Sounds like you are exceeding a rate limit.
Or you don’t meet the requirements to post in all channels. Most channels employ a follower mode, requiring the bot to follow the channel (which is can’t automatically as there is no create follows endpoint).
Or for the bot to hold a rank, such as VIP or Moderator in the channel.
A normal user cannot repeat the exact same message within a given time span.
Low all response messages from the server.
If you do not have the CAPS and TAGS capabilities enabled you might be lacking critical response messaegs and information to help diagnose the issue.