Licensing Notes

"The device with UDI A901:CAT1918U007 not found" - That sounds to me like you have tried to install the exact same license file(s) on both routers. They should be device specific I believe (I actually haven't don't this for an ASR901 but for all others they are device specific).

If you run the command "show license udi" you will see the device model/type/PID and the unique device serial number (SN). Together they make the UDI.

Make sure you are downloading the lic files unique to your devices; go to www.cisco.com/go/license and use your CCO account and the UDI from the command above to generate the unique license files for that device.