QB Issue Resolution:

Same thing happened to us… here’s my fix  go to Gear/Settings/Quickbooks  Labs/ turn on Alternate Navigation with Centers  click done   That fixed it for me, you’ll have to do it for each client company.   Unfortunately, no one at Support had any idea what was going on, they just said try another browser, clear your cache, blah, blah, blah

Resolution for Issue 'The Apps option on the left side menu of my QBO account has disappeared. How do I get it back?' available: Yes (Solved).
Source: Intuit Community forum.

The Apps option on the left side menu of my QBO account has disappeared. How do I get it back?: this 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 issue yourself by looking for a resolution described below. If it is a complex issue or you are unable to solve the issue, you may contact us by clicking here or by using other support options.

Support for another browser
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Error Recovery for another browser [Canada]
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