Messages like this can happen at the end of the render.
Depending on the version of your After Effects you may receive this message. This has to do with the technology used to create the buttons, but it has no impact on your work.
At most, it may be necessary to restart the script, closing and opening it again through the Window menu in After Effects.
After Effects is dynamic software, sometimes in some updates they end up messing with settings that change the behavior of some scripts.
This can cause this type of behavior in Simple Text. Usually the buttons return to normal on their own, but if necessary, close and open the script again via the Window menu in After Effects.
Usually this type of error is also resolved by closing and opening the script again. Sometimes this process needs to be done twice to ensure that the script restarts completely.
The cause of these errors can be the most variable, but in the vast majority of cases just restarting the script already solves the problem.
The script depends on a huge amount of expressions to make it possible to create text animations more quickly and intuitively. This can make your After Effects or its renders slow down when working with many texts simultaneously. The solution in these cases is to pre-render with alpha channel layers or compositions that are already finished. This will reduce the number of expressions being calculated, and make your workflow faster.