fill code from mobile always stays screen

It should just disappear under Normal Operations and no Reboot Required

1 - Restart in Safe Mode. This will perform a Disk Repair, clear cache files and only load Apple Software, extensions and fonts. The boot up will be slow and can take some time - Normal.

2 - Does the issue present in this mode ?

3 - Sometimes a Safe Boot followed by a Normal Boot will just put things right.

4 - If not - there could be something in the main User Account playing up. To further isolate this - Set up users, guests, and groups on Mac. Then log out of the Main User account and log into the dummy account and test again if the issue persists.

5 - If the issue is present in the dummy account - then, this appears to be a System Wide issue on the computer.

6 - If after performing each of the above steps in the order that have been presents and still have issues - please advise for possible further assistance.

7 - Download the Application Etrecheck directly from the Developer.

The application is free or paid from added features. 

It will take a Snap Shot -  both the hardware and software.

 The Report will Not Reveal Any Personal Information. 

Post back the Full Report - copy and paste - >>>> using the Additional Text Icon ( 3rd Icon to last ) <<<<

We can have a look at the report for possible issues and may have possible suggestions to resolve the issues.

To compare - when I login into my Government Income Tax Site - they required their type of Two Factor Authorization.

An SMS is configure to send to my iPhone number like in your above image 6 digest code.

On the iPhone and on Apple Silicon M1 Mac Mini the Messages application both receive the Code

When I click the Code in Message on Computer, the 2FA is completed and Code disappears

I am then permitted to proceed to Log Into the Government Website for Taxes

Thank you for the feedback and keep us posted on how this unfold for steps 4 to 7 - time permitting