Processes in Microsoft 365 for setting up Office apps, redeeming product keys, and activating licenses.
The error code 49 is usually a cached credentials error ,the best option is to perform a full repair of your Office installation.
Open the Settings App (gear icon on your Start Menu)
Go to Apps - Installed Apps, then scroll down to find Microsoft Office
Select that and choose Modify - Online Repair
That should fix any issues with your Office Installation.