Dear Daniel
Welcome to Microsoft Community.
Hello, I'm Linn, here to help you solve your problem. According to the error message prompted by Office2021 in the question, I think this seems to be an error caused by a network problem.
It is recommended that you change the network settings to fix the problem:
- Try to change to another network environment, such as a network hotspot;
- Set the DNS server (remember to reset it to automatic after the problem is solved): press Windows+R and enter ncpa.cpl
- Click the name of the network you are currently connected to, open the Network Status window, click Properties, double-click Internet Protocol Version 4 (TCP / IPv4) in the Network Properties window, change Automatically obtain DNS to "4.2.2.1" and "4.2.2.2", and then click "OK".
- Reset network settings: Enter the following command in Windows PowerShell (Administrator), and then restart the device: netsh int ip reset netsh winsock reset
Please try the above preliminary network solutions. This is not a complete solution.
Please understand that our initial response may not always resolve the issue immediately. However, with your help and more detailed information, we can work together to find a solution. Being patient will be a factor in eventually solving the problem.
Sincerest greetings
Linn |Microsoft Community Support Specialist