Celine's answer is somewhat incomplete/ incorrect (does not account for jusqu'à maintenant, for one). I can't vouch for the veracity of this source, but I finally after much searching found something that actually broke down the actual rules for jusque vs jusqu'à. 

• “Jusque” is normally accompanied by the preposition “à” . For example: jusqu'à la fin, jusqu'au (contraction de "à" + "le") bout de la rue, jusqu'à hier, jusqu'à demain, ...

• “Jusque” is constructed without “à” when it is followed by one of the adverbs “alors, ici, là, où” or another preposition. For example: jusque-là (with hyphen [trait d'union]), jusqu'ici, jusqu'alors, jusqu'où, jusqu'en, jusque chez, jusque sur, jusque dans, jusque vers, ...

• “Jusque” is constructed without “à” with the adverbs “assez, aussi, bien, fort, si, très”, modifying an adverb of time or place. For example: jusqu'assez avant dans la nuit, jusque fort haut sur cette pente, jusque très avant dans le désert, ...

The final “e” of “jusque” is always elided before a vowel , that is to say we erase it in favor of an apostrophe and we paste the following word. As in “jusqu'à" or "jusqu'ici.”

This is adapted from: https://www.orthographiq.com/blog/jusque-ou-jusqua-orthographe where you can find even further help on the matter. Even if they placed it at a higher level like C1, this is exactly the kind of thing I turn to Kwiziq for, and I think they should have a lesson addressing it, since there does not seem to be clarity even among the instructors...