Submission progression will definitely be 100% when you have reached 8 completed submission, whose status will then appear “Awaiting review”. In the meantime it is a varying number that depends on how many active you have and can go down if someone drops out. Anyway, I also would have expected to see 8/8 (or 100%) given that you have 8 Active people. Instead, if I remember correctly the Time taken will be shown only once the submissions are sent out and will be labelled as “Awaiting review” (the Status). In the meantime, it should make sense to see it N/A.
Also, are you able to see if data is being correctly collected from your survey tool?
@Josh may be of help here if you provide him with your study name and your account, he can look into it.
Sorry if I cannot be of more help.