I had something like this happen to me.  Try recreating the Event collector.  If that works, then just delete the bad one.

this did not work unfortunately 

Hi, 

 Please make sure to open Port# 443, it may cause the issue. also make sure to open vmapp ports [9443,5480] to communicate with Discovery MiD Servers.

 Thanks & Regards,

Vinil.

hi Vinil, thanks for the response. 9443,5480 would be on the vCenter end or the MID server?

Hi Ravish,

Open communication from MiD Servers to Target vCenters.

it's always better to open request on Bi directional method.

if this resolves issue, please mark it as correct answer.

Thanks & Regards,

Vinil.