During the installation of High Availability, when you install BizTalk360 primary server with one credentials (say ex: svc1) and on the secondary server with another credentials (say ex: svc2). While longing into BizTalk360 web portal on the Primary server it will work fine, but when you login into the secondary server with the credentials of svc2 you might face the below problem.
To resolve this problem you have to possible solutions:
1. Adding the secondary server user (svc2) in BizTalk360 and changing the BizTalk360 monitoring server credentials to the primary server user (svc1) will solve.
2. Uninstalling and Reinstalling BizTalk360 with the credentials of primary account (svc1) or Installing BizTalk360 under one account in all server.