Email verification doesn't work

I am currently still on the trial version (I sent a request to update the license already), and I would like to test the logistics of the study so I installed the app and made an account myself.

Somehow, I have had to verify my email already three times within the time span of three hours. It seems that the email verification doesn’t work - is this because of the trial version or am I missing something?

I just read in a different post from earlier this year that this is an iOS issue. I seem to be running into the same issue, could this be possible?