Turn the Physiks on Arcade and all shoud be driveable instandly.

When you turn on realistic you have somtimes this bad conditons (normaly in scenarios it shoud be best conditions to play
but at the moment your own settings will make it that way lik it is)

in normal game you coud skip some days or month to have dry ground to work.
and you can see ground conditons in the fieldmenu the best i think is to have fieldwetness under 50% better 30%
to find out at what % wetness you have to try.
i never have probs since scenarios and i did the same turned on Arcade
maybe you coud skip some days in there but i dont know

Just a side note. Did you active 4-wheel-drive because if I remember correctly this is something which should be done in one of the scenarios.

PS:
One of the next updates will show surface water on the field menu and map which is relevant for droving on the field and gives you better visual feedback.

with pressed CTRL key you activate traction with the mouse pointer