That means exactly what the warning says. Open write checks and search for that check number.   You should find the other check.  You can shut that warning off in your edit>settings menu.

Resolution for 'Another checks issue: 'When I go to print checks a window pops up says Problem – Another checks has number ????' available: Yes.

The Another checks issue or error code is a known issue in Quickbooks Online (QBO) and/or Quickbooks. Support for this issue is available either by self-service or paid support options. Experts are available to resolve your Quickbooks issue to ensure minimal downtime and continue running your business. First try to resolve the Another checks issue yourself by looking for a resolution described in the article. If it is a complex Another checks issue or you are unable to solve the issue, you may contact us by clicking here or by using other Another checks support options.

For more information about resolving issues related to Another checks in Quickbooks/QBO or to get support for the issue 'When I go to print checks a window pops up says Problem – Another checks has number ????', click the link below: