Hi.
I could replicate the same problem by registering the CPT late in the init process
If the CPT is registered late, the DeepL settings might be constructed before the CPT is registered and will not save the ACF/meta fields relative to that CPT.
If you can save the ACF fields relative to a CPT (selected blue in the Pro tab) and still not get the ACF fields translated, please contact me (my handle at gmail ) with a few samples or an access to a dev environment so I can investigate specific conditions.