Activities not showing up on groups

Most likely because the privacy settings in your User Profile do not allow showing the activities. You have to adjust it to match your needs.

The privacy settings for activities was set at "my connections and groups"

And what about your Privacy Zones? Did you define any? If your activity was within one of the privacy zones, it won't appear anywhere, regardless of the activity privacy setting. The privacy zone has a stronger priority.

What do you mean by privacy zones? i do not see that listed.

Look at the bottom of the page Privacy Settings

Ok, I found that, but I do not understand it at all. Can you explain it better for me please. I do not want to share my location with others. 

If you do not want to share the location to others, the activities within the private zone won't be shared. If you want to share you activities, you either have to make them out of the private zone (at least partially), or you have to make the zone smaller. However, if you make it too small, people will be able to pinpoint you approximately at the center of the zone anyway.

Ok. But what if I am running on a treadmill at my home? I am not actually going anywhere.

That should not matter - normally there is no GPS position stored with that kind of activity.

Well I can't remember all the ones that were missing, but sometimes I record a walk and it shows up and other times I record a walk (same route) and it does not show up under the activities tab with the group. Sometimes it will be under the steps tab because it has my total steps for the day, but not my "activity". Sometimes I go skipping with my kids, and I record the name of the activity as skipping and put it under the category "other" and that will not show up either.