It turns out that my issue was based on a misunderstanding. I am not permitted to trade TLT for the reasons given above but I am permitted to trade TLT options. Thankfully I can still follow the SteadyYields trades.
I trade using IB (I am in France) and I never met this kind of issue. From my experience, it turned out that they always replied to me when I add a problem, even if it was with a certain delay by mail. You can also directly call them and ask.