@Iniobong can you share a little bit more details about the error you're getting when loging through the mobile app ! its possible your Microsoft 365 administrator has a Conditional Access policy in place that prevent users from accessing M365 products such as Teams, Word, OneDrive...etc. on personal mobile devices or on any mobile device in general.
are other users able to access MS Teams on their mobile app ? did they have to go through and register the device in your M365 tenant to comply with any MDM/MAM policy ? usually, if a Mobile Device Management (MDM) policy in place, users have to download the company portal app to register their phone in the organization tenant and once they agree on all terms & conditions and download the MDM profile, they will be able to access company resources on a personal device.