When I add a new user as Admin, QuickBooks asking to verify my account, then the page is redirected to reset password, and back to the same cycle, without adding new user

Hi ca21:

This definitely sounds like something you need technical support to help with.  From within QBO if you click on help, there's a "Contact Us" button on the bottom where you can enter your phone number and they'll give you a  call back - I typically only have to wait about 5 minutes usually.

Once they call you, they also have the ability to share screens with you, and you can show them the problem.  If they can't fix it on the spot, they'll definitely come up with an answer for you (support at QBO is super helpful).

Hi ca21, 

Thanks for reaching out! Given you've already tried some great troubleshooting, I strongly encourage you to get in touch with our tech support team. Our agents will be able to thoroughly look into this to help you get back on track. Here's how to reach us.

Schedule a Callback or Chat: click (?)Help in the upper right > type and enter "Contact support" into the QB Assistant > click Contact Us > explain your situation > click Let's Talk > choose Get a callback or Start a Chat. Support is available from Monday to Friday between 9 a.m. and 8 p.m. ET.
Social Media: Facebook, Twitter, and Instagram from Monday to Friday between 9 a.m. and 8 p.m. ET

All the best to you!