This is most likely a compatibility issue or how the QuickBooks Online (QBO) app reacts with the recent software update, djbalaam.
I recognize the benefits of being able to rotate your device into landscape when editing your invoices. Since this is how the application interacts with the update, you can use the web version of QBO through your tablet's web browser. This way, you can continue working in landscape mode.
I'm still ready to back you up for more queries about your invoices or with the QBO app. Feel free to comment back, and we'll get back to you for more help, djbalaam.