Since last year, they have been sending notifications to users of outdated QB Desktop (e.g. 2018) to create an Intuit ID account and connect it to your company file(s). We may have to download the latest installer file and reinstall our QB program to fix this issue. If you are still having problems and only need one user to access QB Desktop, you can use the trial version of QBD 2021 to upgrade your data and use it for good if necessary.