Users registration

Hello,

I have a problem, when i do a registration test with Ultimate member’s form. I fill up all fields, enter a valid e-mail, it works. When i try to delete this registration from Users and so delete this e-mail it works too. But when I try to do a new registration with the same e-mail it says that “this e-mail is already use” and this e-mail doesn’t exist anymore in Users’ database because I have just delete it. Have someone a solution please?

And I have an other question, is this plugin compatible with plugin “WP member”?

Thank you for your help!

https://www.ads-software.com/plugins/ultimate-member/