Form is pretty out of date. The current version is 2.4.1. My first suggestion is to update it to see if that resolves the issue.
fyi, I did a test submission and I too received the success message. Please check to see if it is in the moderation queue. If it is, then things are working well and perhaps your test did not work because you were logged in when doing the submission. Entries added while logged in as the admin will not hit the mod queue as they are submitted using the same user permissions as you have in the admin.
Now, if my test submission is not in the mod queue, like I suggested, try updating first. If that does not work, then I’ll need an admin account to debug further.