You’ll have to leave the organization you created before being invited to join another one. Follow these steps to leave your own MaintainX org:
Mobile:
Click More in bottom right corner
Under Organization name, click View Settings
Click Teams/Users
Click arrow to right of name
Click Remove from Organization
Click Remove to Confirm
Web:
Go to Teams/Users tab
Click name
Click Leave Organization at bottom of profile
Once you have left your MaintainX org, you will be able to accept your company's invitation to join the company's MaintainX org.