QB Issue Resolution:

GO to the Company Gear (upper right hand corner)

Select “Company Setting” under Setting
Select “Sales” under Settings (or “Sales Form Entry” under Preferences)
Check-box “Custom transaction number” (see attached screenshot below for reference)
SAVE
GO back to create new Invoice

Click “+” plus sign
Select “Invoice” under Customers
Enter new “Invoice no.” (located at top right corner)

Resolution for Issue 'how can I alter the invoice numbers?' available: Yes (Solved).
Source: Intuit Community forum.

how can I alter the invoice numbers?: 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 Invoice
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Error Recovery for Invoice [Canada]
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