Thanks for joining us, @Alex319.
I have some information about switching off the Dark Mode theme. Let your user switch off the Dark Mode by following the steps provided by my peer @LieraMarie_A . After performing the steps, have your user log out and log back in to see the changes.
If they're experiencing the same result, please contact our Customer Care Team so we can create a ticket for you and investigate further. Refer to the above steps to reach out.
I'm attaching this link in case you need help in managing your QuickBooks Online (QBO) account: View all articles for QBO.
If you still have questions about your account, drop them in the reply section and I'll be happy to answer them for you. Take care and stay safe.
