VPN with certificates

Hi all, im experimenting with a mikrotik routerboard 751U 2HnD. I have succesfully created a vpn with pre-shared keys.
When i change to rsa the vpn just doesnt work anymore, the error i get in the mikrotik log is: “fail to get peers cert”. I couldnt find anything in google about it.
The VPN is between the mikrotik and a cisco 2800. in cisco 2800 the log shows phase 1 complete but then gives timeout waiting for the mikrotik.
thanks in advance!