It might be that your track can still count as part of a Challenge despite being initially excluded. There are several options available (depending on the reason your track was considered invalid in the first place) and you can fix certain errors yourself.
In cases 1. and 2.
Your average or maximum speeds were too fast to be one of the selected activities. Could it be that you accidentally continued recording after you got back into the car? If so, you can crop your track accordingly to delete the invalid section. The option to do this can be found in the editing section of the track on the web and in the app.
In case 3.
The activity you recorded was not one of the Challenge's permitted activities. You are able to subsequently change this. To do so, go to the editing section of your track on the web or in the app and change the activity to one that is part of the Challenge.
Unfortunately, there aren't any solutions to help tackle the other issues. If the problem appears to be technical or without obvious reason, please contact our support.