Unable to initialize gtk, is DISPLAY set properly?

Trying to get an app running under rl9 compatibility mode. The app was installed using rpm2cpio, apparently successfully, but I get the above error trying to run it (chrooted, of course).

I have confirmed that gtk4 is installed. I have confirmed that the $Display variable is set to :0.0. I have run xhost+ before I run 'sudo chroot /compat/linux bin/<app name>'

Same problem if I chroot in to a shell session first, then try to run the app.

Is there something further I need to configure in rl9?

Thank you.