visokaposlovnaskola.edu.rs needs to be available in both Cyrilic and Latin script (Standard Serbian language uses both).
Currently, all the content of the website is served in Serbian Latin script.
I want to add the option to serve the current content in the Serbian Cyrilic, also. Both Serbian Cyrilic & Latin (Location: Serbia) are available to select from the WPML setup option *create a custom language.
When i click on the button Save language, i get the *The wrong format in fields *Default locale and *hreflang.
The same error is showing regardless the selection of Serbian (Cyrilic) or Serbian (Latin).
Is there any documentation that you are following?