Problem when using different machines to complete challenges


I’m using two different computers (one is my private and one from work) but the problem is (and I haven’t found a solution yet) is that when completing some challenges using computer at work, they are not completed when I want to continue later at home, with another computer. On the map, it shows they are done, but when I open one to check, my lines are missing.
Is there a specific reason that is so or could I (I dont know, sync it somehow). Because, all the challenges are online, not local, so it should not matter, if I log in from different machines.