Background of the issue:
I am working on a site under development, 'cargoisking.com', and I want to change the hreflang from 'de-at' to 'de-AT'. I am trying to do this in the WPML settings under 'WPML -> languages -> Site Languages -> edit language'. I am following the documentation at https://wpml.org/forums/topic/modify-hreflang-tags/.
Symptoms:
When I attempt to change the hreflang tag, I receive an error message: 'There has been a critical error on this website. Please check your site admin email inbox for instructions. If you continue to have problems, please try the support forums.'
Questions:
Is it possible to change the hreflang from 'de-at' to 'de-AT'?
Does the error have something to do with limited access to WPML because it's a copy of our website?