Agree if concerned about a possible hack, official EA support is the place to go.
FYI, I checked (one of) my accounts, and no issue. But some questions/comments (both for general audience here, and if you take to EA support):
1) Did you retry hours or a day or two later? Maybe it'll solve itself.
2) PC or which platform?
3) Your change in challenge status - was this from in-game, or as seen in N7HQ, or both?
4) All challenges got reset? Ones that were complete and ones that were in progress?
Note:Normal procedure is when a Mastery is completed, all the ones under that Mastery are reset. The ones that were just partially completed should keep same status. I don't think this is what you are talking about, but mention just in case.
5) Cloud saves? If PC, did you get a message about cloud and local being out of sync?
Both on n7 hq and in game but also it’s saying I’ve actually completed a challenge even though I know I haven’t finished it as well
The only "dylan881" I see in N7HQ is listed as on PC and N7=1 with no MP play yet.
Playing on a different account? (assuming you only have 1 account)
I’m on Xbox mostly myXbox gamer tag is Guestclone wars
I took a look at your N7HQ. An old-timer returning to the game? Given your hours, the L10 Eagle made me ... 🙂
Okay, I'm going back to my #4 (in post #6)
The only Masteries you've completed are Squad Elite, and AR Mastery.
FYI, Squad Elite is the only one that doesn't reset when "completed" (well, that and "Mass Effect"). Every other one does. For AR Mastery it is completed when you achieve 9 of the group's AR challenges. Which are all listed as completed once in your N7HQ. Once you completed AR Mastery, those 9 got reset. That includes the M-7 Lancer (is that the "M 7 gun" you referred to in OP?). This allows you to get the Mastery multiple times. That's how it's supposed to work.
If that is indeed what you are seeing, all is normal.
