When upgrading to 8.7.1, the Install Readiness Check may prevent you from continuing with the upgrade due to Microsoft Report Viewer not being installed. You may already have Microsoft Report Viewer installed, however, this check still comes up.
With the release of 8.7.1, Microsoft Report Viewer 2015 is required, whereas it was 2008. In addition, there is a prerequisite to install Microsoft SQL Server System CLR Type before installing Microsoft Report Viewer 2015 Runtime.
Upgrading to 8.7.1
Prerequisites are not installed.
Please click on the About Microsoft Report Viewer link in the install readiness check. This will then take you to another webpage with links to download the prerequisites.
Other Notes:
.NET 4.8 is also a new requirement for installing the SMP and also Site Servers.
If a Reboot is needed, you will not be able to pass the Install Readiness Check. Please reboot before starting the upgrade. And of course login as the App ID when doing the upgrade.