This error normally happens when you are installing BizTalk360 on a standalone server trying to point to your remote environment. During installation, the installer picks up the BizTalk management database name and location (SQL Server instance name) from the registry. If it's a fresh server, these information will not be available and the configuration tables are populated with blank values.
The quickest way to fix this issue is by entering the values manually in the BizTalk360 database.
- Open BizTalk360 database using SQL Server Management studio
- Navigate to BizTalk360 database > Tables, right-click on b360_admin_BizTalkEnvironment and select Edit top 200 rows
- Enter the correct values for BizTalkMgmtSqlInstance and BizTalkMgmtDb