Since upgrade to 5.34, Drupal accounts are not being created when a member signs up
We figured out a fix for this yesterday (it was reported yesterday as a wordpress issue)
There is a patch here
https://github.com/civicrm/civicrm-core/pull/19696
It will be part of 5.35.0 which will be released on Wednesday
If you are not comfortable patching and can't wait 2 days the other option is to upgrade to the rc version of 5.35.0
https://download.civicrm.org/latest/
(it won't change that much over the next 2 days but you can update the code base with the released version when it does drop)