Hi there,
Accounts that have been inactive for 3 years are permanentely removed from the database. This is required due to the global GDPR ruling (privacy laws). So if it is already more than 3 years ago that you last logged in to your account, then it will be removed.
You could try going to our customer support and ask for a definitive check with the e-mailadress that you had linked to that account. They can verify if it still excists or not. You can find our customer support using the below link.
https://support.onlinesoccermanager.com/hc/en-us
Then click on 'submit a request' and choose the option 'OSM' to fill in the contact sheet.