I was stuck with the same issue, where my QuickBooks stopped working. I also identified some common causes of this problem, including a company name that is too long and a damaged or missing QBWUSER.ini file. So, the question now arises: what can we do to resolve this issue? Here are some of the troubleshooting techniques I used to resolve the issue.

First, we need to run the Quick Fix my Program, which can be accessed through the Program Problems section of the QuickBooks Tool Hub. If this doesn’t work, we can run the QB Install Diagnostic tool from the same. Still facing the error? Then move to the third solution, which is renaming the QBWUSER.ini file. To do so, right-click the QBWUSER.ini file and add old at the end (QBWUSER.ini.old). These troubleshooting methods have helped me, and hopefully, they will help you too.

https://proadvisorsolutions.com/blog/quickbooks-not-responding/