Unable to see or complete other missions

on challengers I have missions to complete, last count 6, like, complete last 3 main or side missions in the Marshlands region, progress 1/3.
South coast region 2/3.
North coast region 2/3,
Mountain region 1/3
Forest region 2/3
Farmland region 2/3
I gone to these regions and walked round look to see if something will trigger them but no.
so how do theses mission show them selves to complete them ?

Check your LOG and see if you have some uncompleted missions there.

Yes fuel to the fire which I posted about unable to loot the tank complete it 3 time and the tank respawns when I close the game for the night.
And the Bike ride mission which I am doing but keep missing the time by a few seconds.

you just need to go around not only the region. it sometimes shows a mission symbol 10 meters from the subject. I had such a problem in the achipelago region. it turned out that the task was 30 meters from the house

To get side missions, you need to pick up specific mission item to start the side mission.

Here is the list of main/side missions in the game (except FNIX Rising DLC missions),
link: https://generation-zero.fandom.com/wiki/Missions

Compare your mission log with that list and look what side missions you’re missing.