Hi. I'm Brian and I'll try to help.
This forum is dedicated to problems with Outlook for Android, which can be used with any mail service. Who is your mail provider? The mail provider determines the rules about how frequently you must log in.
If you use a Microsoft account, the Microsoft Services Agreement applies. Here is a quote from that agreement, section 4.a.ii:
"Account Use. You must use your Microsoft account to keep it active. This means you must sign in at least once in a two-year period to keep your Microsoft account, and associated Services (unless specified otherwise), active, unless a longer period is provided in the Microsoft account activity policy at https://go.microsoft.com/fwlink/p/?linkid=2086738 or in an offer for a paid portion of the Services. If you don’t sign in during this time, we will assume your Microsoft account is inactive and will close it for you. Please see section 4.a.iv.2 for the consequences of a closed Microsoft account. You must sign into your Outlook.com inbox and your OneDrive (separately) at least once in a one-year period, otherwise we will close your Outlook.com inbox and your OneDrive for you. If we reasonably suspect that your Microsoft account is at risk of being used by a third party fraudulently (for example, as a result of an account compromise), Microsoft may suspend your account until you can reclaim ownership. Based on the nature of the compromise, we may be required to disable access to some or all of Your Content. If you are having trouble accessing your Microsoft account, please visit this website: https://go.microsoft.com/fwlink/?LinkId=238656."
So, how long has it been since you last logged in and do you have a subscription to a Microsoft service using that account?