The German LBA doesn't accept the FAA "English Proficient" on a certificate "because it has no test date" and consequently no expiration date. Doesn't matter that I have an American passport...
So, I went through a similiar, sometimes humorous experience as above as I worked to get German recognition of my FAA license. I had to have a minimum of Level 4, of course. As an American I thought it was funny that I would have to prove I speak English, but I can speak German-as-a-foreign-language on the radio without "proving" I speak German!
One of my club's members is an approved tester for people who have existing/grandfathered Level 4 proficiency, but cannot do initial tests or anything higher than Level 4. He eventually learned there are now provisions to prove one is a native speaker and get Level 6 that way. If I had been able to documentat that I had spent the first ten years of my life in a country where English is an official language, I would not have needed a test. Three thousand miles from home, that is hard to prove, and I'm not even sure if I could readily prove that at home.
So, I paid 100 Euro for an evaluative interview (by a Brit - how can he evaluate my English?!) to determine that I am, indeed, a native speaker. I did get a bit of a rebate; the tester bought my Chinese dinner.
That's my story, but what I wanted to mention is that I thought I saw some rule during my research that the tester has to be licensed by the same country that issued your license/certificate. Is that true?
Terry