QB Issue Resolution:

turn on inventory

gear>settings>company settings
sales>products & services

the gear>settings>products and services>New

see the pic

Resolution for Issue 'how do I enter my inventory' available: Yes (Solved).
Source: Intuit Community forum.

how do I enter my inventory: 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 Inventory
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Error Recovery for Inventory [Canada]
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