QuickBooks Validation Code in Registry or The Service is Temporarily Unavailable

Turn your QuickBooks off.
In the taskbar, open settings and then open date and time settings.
Now, synchronize your date and time settings.
Select Apply and then select OK.
Now, turn your QuickBooks Desktop on and then open Help option –> now, activate your QuickBooks software and then click on Activation.
Now, retrieve validation code and then enter.
Now, click on next.

Rename MSXML file-
If you have 64-bit Operating System, activate MSXML with the help of following command:
Open Start Menu, once it opens, type CMD
Right click and run it as administrator.

For Windows 8, from keyboard, use windows key and then enter cmd.
Right click and run it as administrator.

Open command prompt, enter the path cd\windows\syswow64 and then hit enter.
Now, enter keyword regsvr32 MSXML4.dll, press enter again enter regsvr32 MSXML6.dll and press enter.
For 32-bit Operating Systems: Use the command we are mentioning below to register MSXML file.
Use Windows + R to run Windows command.
Type CMD and then press enter.
Type regsvr32 MSXML4.dll, press enter, type regsvr32 MSXML6.dlland then press enter.
Run QuickBooks Install Tool is made up of certain complex processes. To handle such scenarios, we have team of technical experts who can handle your software promptly.
Rolling out old windows user is a better choice. For that, we suggest you make a new windows administrator.
Make a new Windows Administrator.
Now, install QuickBooks once again – this is the last step. All you have to make sure that you fill all the relevant information at the time of installation.