Confirmed at least three times now that skill drain and similar cards that negate face up monsters effects have also stopped a Tuner being able to Synchro Summon. The simulator is DevPro. Is this suppose to be happening or is it a glitch? And if so how to report it?
The Artistic Kamen Rider
That has to be a glitch/bug on DevPro, because Skill Drain & other Monster Effect Negation cards shouldn't negate Synchro Summoning. I'd like to point out not all Tuner Monsters have "Effect Monster Orange" as a few have "Normal Monster Yellow" like Tune Warrior, Ally Mind, & Water Spirit...that is to say are naturally tuners, there are also cards that can make monsters into Tuners as well.
If your opponent had a Continuous Trap Card "Discord" face up on the field, then it stands to reason you're unable to Synchro Summon because of it.
instantly_oatmeal
Cards that negate effects will not stop a Tuner from being a Tuner. Being a Tuner is a part of being a card (like its Type. You wouldn't be able to "negate" a Blue-Eyes White Dragon from being a Dragon-type, for example). After all, there do exist Normal monsters that are Tuners. If being a Tuner was a negate-able affect, all Tuners would be Effect monsters.
So yeah, glitch UNLESS something else is stopping you from summoning...