QB Issue Resolution:

If you mean can you have more than one subscription to QBO with one login, yes

Go to  http://quickbooks.intuit.com/pricing
Click Buy Now under the version you need.
Click Already have an Intuit account?  Sign In.
Enter your log in information and follow the on-screen prompts to set up the second company.

Then when you sign in to your account you will have the option to enter “Company 1” or “Company 2”

Resolution for Issue 'about adding multiple company in a single account' available: Yes (Solved).
Source: Intuit Community forum.

about adding multiple company in a single account: 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 Company
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Error Recovery for Company [Canada]
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