This relates to EASA (Europe).
The licence / ATPL is issued for life and remains valid irrespective of medical status. Without a medical certificate you cannot exercise the privileges of most of the ratings with the exception of the Synthetic Flying Instructor (SFI) Rating and Synthetic Flying Examiners (SFE) Rating.
Essentially an SFI and SFE rating is the same as a TRI and TRE rating (simulator only) and so you can do training and examining for initial issue type ratings, instrument rating renewals, licence proficiency checks, etc. So within EASA you can certainly examine in the simulator without a medical certificate.
Many older and bolder TREs and TRIs cashed in these ratings for SFI and SFE ratings so as to not have to continually pay the licensing / administration fee changing from one to the other as their medical status changed from month to month.