If you are facing any problem in changing the service account for BizTalk360, please make sure whether the service account (the one used by IIS Application pool and Monitoring NT Service) has the Administrator rights on each server to fetch the data. The service account will query the NT Services, disk information, and so on from the server. 

You also need to reset IIS if in case you add any account to a corresponding group. If you do not reset IIS, the changes will not get effected.