Seems odd that you cannot use same bank login but different account for company B
But QB or the bank may restrict use of login to one entity other than you.

Can you get your bank to split off account B with a different access login? Inconvenient for you since […]

Resolution for 'access login issue: 'Is it possible to link my bank client account to two different Quickbooks accounts? I’m trying with RBC and it’s not working (Error 103).' available: Yes.

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

For more information about resolving issues related to access login in Quickbooks/QBO or to get support for the issue 'Is it possible to link my bank client account to two different Quickbooks accounts? I’m trying with RBC and it’s not working (Error 103).', click the link below: