Your frustration is very understandable. I know how exasperating it is to spend hours looking for the start of a thing you have to do before you can do something else. 
OK. That was the thing I didn’t understand.
I presume you selected Tiragarde from that map in the first place? Or did you just find random quests around Tiragarde?
Your armoury says you have the Come Sail Away achievement of arriving at and meeting the people of Boralus, but that was a week ago. Did you come to Boralus and do all the unlocks on that character, or a different one?
You have your Heart, also from a week ago. Again, same character?
And, uh, now Ithink of it, is it your level 70 that you’re posing on here that has the problem? Because if it’s a different character, we’re chasing the wrong road. Other commens say that the map requires Level 25 now. I hadn’t heard this before, but I imagine it’s possible, so if you are on a low-level, that could be a factor.
Failing to pick up a quest can also be caused by addons. Probably not, in this case, but worth Disabling All addons and trying the Scouting Map again.
WoW Support says you have to make some progress in one zone before you are able to start another, but you have done that
They also list a bug from 8 months ago, with no stated resolution.
One comment I found on Reddit was that someone went to Stormwind, turned War Mode off (or on) and was able to interact with the Scouting map when he returned.