There’s no distinction between users and vendors on the registration step, vendor profile is created when the first listing is added. Please try to submit a new listing, and check if vendor appeared in WordPress/Vendors section.
The issues you describe seems to be related to caching or conflicts with other plugins, if these were the common issues (random redirects and broken registration), there would be similar bug reports. If these issues remain after disabling plugins and caching you can send temporary WP access to support@hivepress.io and I’ll check them.
