The reset times for the Daily challenges and for the Free Daily Gift in the Shop don't match. This is a known issue which will be resolved in a future update.
Currently, the Free Daily Gift in the Shop appears again every day at 00:00 AM UTC whereas the Daily challenges refresh every day at 03:00 AM UTC.
As a result, if you collect the Free Gift between 00:00 AM UTC and 03:00 AM UTC, you will only be able to collect the Free Gift between these two times on the next day, it leaves only a 3 hours time frame for you to collect the Free Gift after it appears and before the Daily challenges reset.
The best advice we can give you is to collect the Free Gift before 00:00 AM UTC or after 03:00 AM UTC and not in between these two times.
We thank you for your understanding and we apologise for the inconvenience caused.