Hi RCV,
Thank you for your suggested solutions. However, they seem to be generic cookie cutter solutions and have not taken into account my specific situation ie Quickbooks was working fine back in December on the same computer, that our Quickbooks version is indeed up to date as noted in our initial question. We do have Microsoft Edge installed. We've also ran Quickbooks Tool Hub for Program Problems and Diagnostic Tool and ran File Doctor. Also have gone through the steps in 'Can't open your company file in Quickbooks Desktop'. None of them worked. This is quite frustrating really.
