I just tested and twitter hashtags work for me in the new version.
You need to be more specific as to the version where it worked if you can tell it in number that would be great otherwise we go blind.
I could check it by rolling back to the previous version and checking if it works.
If it does tell me the version number
FS Poster - WordPress Social Auto Poster & Scheduler
v 5.3.3 – 17 May 22
This one was working fine, please rollback to this one and check