You can run into issues with showing the translations for strings if you define a locale using a hyphen (dash). For example, a wrong way to define a French locale would be to use fr-FR.
The correct way would be to use an underscore instead. In our example, you should define a French locale as fr_FR.
On the WPML -> Languages -> Edit Languages page, you can set default locale in two ways:
– IETF Language Tag: uses a hyphen
– ISO 15897: uses an underscore
Since the latest changes in WPML String Translation, the use of the hyphen (or so-called dash “-” ) is not possible and should be avoided.
If you have a language that is defined in the format like fr-FR, you should immediately change that to a format like fr_FR so that you can use the translation features of WPML String Translation.