Hi, yes we have found the solution ourselves. It is the pre-installed Dell Optimizer app causing the issue. Launch the app, turn off all the settings, then go to control panel and uninstall it. 
Hi everyone, Hopefully someone is able to help me with this or may experiencing that same issue that we are encountering. Because we are running out of ideas on what would caused this issue. I am an IT Specialist for my company. We are having issue with our Dell Latitude laptops (5410, 5420, 5520) at the office where Microsoft Office apps will disconnect from the server and will not connect back unless the computer is restarted. Once restarted and after few hours and it will lost connection to the server again. Laptops that are affected are on Windows 11 and we do not have any custom images. However, so far this does not happen to all our Dell laptops that's on Windows 11 or other brand of laptops like HP or Lenovo while they are on Windows 11 as well. All other apps (Chrome, Edge, etc.) works just fine without any connection issue. Microsoft Office from www.office.com will work just fine as well. For example, Outlook will stopped connecting to the server and have a message on the bottom right that said "Trying to connect", but it will not connect even after more than +5 minutes. Selected "exit" on Outlook, try to relaunch it, Outlook will not launch and it will just stuck on "loading". Word and Excel will stopped working too when you have a file open and trying to save it to OneDrive. Basically all MS Office apps just stopped working while this happened. We have attempted to run quick and online repair, and reinstalled MS Office but problem persist. Provided users who are affected with a brand new Dell laptop and they still getting the same error. We confirmed the laptops are on the latest BIOS version too. I have contacted Microsoft Support and has been going back and forth with them for a month and half now, but they are still unable to figure what have caused the issue. We are leaning towards Dell as the issue only happens to the Dell laptops that we have in the office.  
Dell Latitude - Microsoft Office apps constantly lose connecting to server