With release of ACFML 1.2 we decided to handle translation of ACF Options Pages with String Translation. After providing values on the option page, you have to WPML String Translations screen and translate their values. After getting client feedback, we're reverting this change.
When we made this change in ACFML 1.2, we didn't realize that it doesn't cover all the kind of ACF options that you need to translate. As a result, some sites have lost translations for some ACF options. Of course, we're sorry about this and we're acting now to fix it.
The next release of ACFML reverts on this change. You will be able to use again WPML's language switcher to translate ACF's Options pages.
If you've already created translations using String Translation with ACFML 1.2, don't worry. After updating ACFML to version 1.3, all your options strings and their translations will be migrated to the old format.
We will be releasing this update during this week. We just released ACFML 1.3, which resolves the problems and adds support for new features in ACF 5.8. If you're missing anything between ACF and WPML, or something else broke, please let us know so that we can handle it quickly for you. Leave your comments and we'll get back to you.