QB Issue Resolution:

To turn on inventory tracking first:

From the home page screen > Click the Company Gear (upper right corner) > Settings > Choose Company Settings > Sales (left side) > Products and Services > Click “Track quantity on hand” ON > Save/Done

Of course, you need PLUS plan to have Inventory feature in QBO.

Resolution for Issue 'a perpetual inventory system in quickbooks' available: Yes (Solved).
Source: Intuit Community forum.

a perpetual inventory system in quickbooks: 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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