Environment
Retain Unified Archiving 4.x
Situation
On selected devices, the RetainService app version 4.9.0.0 has been installed according to the documentation.
After the email with the activation link has been opened, the registration process fails because of the error: No app was found to open the selected link.
Resolution
For specific devices, when that error is received, the device will never be able to be registered via the email activation link. The device manufacturer is able to modify the operating system and something in the modification has prevented the email registration link from being able to associate it with the installed RetainService app.
It has nothing to do with the version of the RetainService app or the operating system version on the device. If you have two different models of the same device running the same OS version and RetainService app version, one may work and one may not.
The workaround is to use the email registration by JSON that is included in lower down in the documentation.