The following error details are in the upgrade log:
The report server database is not a supported compatibility level or a connection cannot be established. Use Reporting Services Configuration Manager to verify the report server configuration and SQL Server management tools to verify the compatibility level.
The report server configuration is not complete or is invalid. Use Reporting Services Configuration Manager to verify the report server configuration.
The report server has already been upgraded to 2016. The report config app on the report server looks normal. REPORTS in this database continue to WORK properly before and after the report server upgrade to 2016.
We've deleted the account on the database and report server and re-added it. We've re-selected the "ReportServer" database from the report config app and ran "Test Connection" with success. We're using the same domain account that was in use for 2014.
The report server has 2 instances. We've applied the above attempts to both.
The last step will be to take out the existing ReportServer database and use the report server config app to "Create New" ReportServer database. However, we would like to avoid this as we would have to manually re-deploy hundreds of reports to the server. ( And it might not solve the problem. )
Any ideas would be appreciated. Thanks.
Please see this link https://www.spiria.com/en/blog/web-applications/understanding-sql-server-compatibility-levels/ for different compat levels and I suggest you set your ReportServer to the same compat level as the master DB on each SQL instance.
For future upgrades my advice is to always run the upgrade adviser/assistant as this will show you prior to upgrading all issues from critical to trivial https://docs.microsoft.com/en-us/sql/database-engine/install-windows/prepare-for-upgrade-by-running-data-migration-assistant?view=sql-server-2016