Hello there, @info-ahl-ltd.
I'm here to share details about the application error you've encountered while using your QuickBooks Online (QBO) account. This way, you'll be able to update your account information and continue using the program in managing your business.
The message "An application error has occurred while processing your request: -90" usually appears when you're trying to update your company details and you're not using the Master Administrator's credentials.
The master admin has access to every feature in QBO. He/She is the owner of the business who originally created the QuickBooks account. If you're the master admin of the company, you need to use your login credentials so you can update company information. However, if you're not the master admin, I'd recommend asking him/her to update the company details. This way, the application error will be resolved.
Furthermore, to learn more about the different user types and levels of access in QBO, kindly refer to this article: User types in QuickBooks Online. It explains about the types of billable and non-billable users in QBO.
Please let me know if you have other concerns. I'm just around to help.
