Problem setting up DKIM on Virtualmin

I have a problem for setting up DKIM on virtualmin.
I have installed DKIM un emailmessages.

When I check the source of email I get the following error:
dkim=neutral (bad format)

I have reset DKIM by removing and installing it again as follows
Signing of outgoing mail enabled? YES
Selector for DKIM record name=2013
Size of new DKIM key=2048
In fact everything was filled out automatically

What can be wrong? I am not an email/ dns expert.
Thanks so much in advance!

Nobody can help with this?
I have posted more details here:
I am very sure that somebody with DNS knowledge can easely solve this problem. Thanks in advance!