You do not need to re-import, downloading from strava works just fine.
- when synchronizing from the share menu change the dates (by default it has to/from for last month) and press refresh to get a full list.
- the auto sync at startup will only look for files in the last 30 days.
There are reports of Strava rate limiting at the moment due to high demand from our users, so it might be worth trying again later (if that is the root cause of the problem).
Mark