Running the QuickBooks Installation Diagnostic Tool as a second solution
Begin using the Quick Books Tool Hub, as previously mentioned.
The Quickbooks Tool Hub allows you to troubleshoot installation issues.
Click on the 'QuickBooks Install Diagnostic Tool' and allow it to run for some time; if any anomalies are found, it takes around 20 minutes to fix them.
Restart the PC once it is finished. you may read here : https://mamafishsaves.com/quickbooks-update-error-1603/