user access to jira ticketing lost

[IT manager Admin]

Hello, need bit of help here. I had customer on ticketing working great, recently for one of the projects this customer has been invited to team of users, using same e-mail account it has created new account, user has lost access to all tickets and ticketing, you can still allocate this customer in ticketing, but user/customer cant access the tickets any more. Can see both account on the Jra ticketing. can't access old customer account as it is saying it was deleted or user details not there. Is there any way to do anything to restore access to jira ticketing under same e-mail address, as user is still working with us, and there is no chance to use different e-mail address

[Nic Brough -Adaptavist-]

What are you using for user accounts?  Is it Atlassian Accounts, Google or Atlassian Access?