You can put it on as many computers as you want.  But if you are trying to use it as multi user, you need difference licenses to do that.

Resolution for '2105 pro issue: 'how many computers can I load 2105 pro on?' available: Yes.

The 2105 pro 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 2105 pro issue yourself by looking for a resolution described in the article. If it is a complex 2105 pro issue or you are unable to solve the issue, you may contact us by clicking here or by using other 2105 pro support options.

For more information about resolving issues related to 2105 pro in Quickbooks/QBO or to get support for the issue 'how many computers can I load 2105 pro on?', click the link below: