Hi Magnusonk,
To ensure that Screen Time is properly configured, verify that Block at Downtime is configured per Use Screen Time on your iPhone, iPad, or iPod touch:
"Block At Downtime. When you choose this setting and you click Ask For More Time when Downtime starts, entering the passcode allows you to approve the app for 15 minutes, an hour, or all day. Child accounts can click One More Minute once, or click Ask For More Time to send their request to the parent account for approval."
Note that this function requires that a passcode be configured in Screen Time for this to operate.
If that feature is already configured, changing the Screen Time passcode to one that is not easily guessed by the device user may be necessary.
If those don't help, reach out to Apple Support directly to investigate further.
Regards.