If you are seeing an error message when you are trying to create or edit accounts in Mayday HQ, it's likely because you need to re-authorise your Xero connection to give Mayday permission to make these changes.
You will see a banner at the top of your screen like this one:
Simply click the Re-authorise link and you will be redirected to reconnect your orgs and update the permissions.
Once this is done, you should have no further problems and you wont need to do this step again.