Our team is having a look at this. The workaround mentioned in the post here is one way around it. The other is to finish setting up GiveWP's Text-to-Give add-on, because what's going on here is that it's looking for the Post Title of the form you designate for Text-to-Give donations, and returning an error if that field is empty. By completing the connection to Twilio, and then selecting a Donation form, this problem is averted.
Definitely annoying, but with these two workarounds, this issue is not terribly urgent.