You mentioned in the previous post that it was tied to a Teams (Microsoft?) account.  If you have been deprovisioned from that enterprise then you would need to contact that company to get access restored. 

Otherwise double check you are logged in with the same account that created that base.  

After reading other comments on this, it sounds like you may have been part of someone else's team plan and they deleted/deactivated you from their team plan.  If that is the case, you would need to reach out to the owner of that team to have them transfer the base back to you.

Thank you! the team leader gave me access again I can see the spreadsheet. How can I separate my spreadsheet from the group and have my own account?

You will need to copy it to a workspace you own: https://support.airtable.com/docs/transferring-ownership-in-airtable