readycloud : media backup getting certificat path not found.

Help please.

have just got new phone and installed readycloud.  this was all working OK on previous phone - media backup to my readynas server working fine.

now when I try media backup, I get error:  "trust anchor for certification path not found".

I have searched for this error on various sites but the correction actions for this error are way above my knowledge and expertise.

can anyone help with a simple solution to this problem. I dont know where to start.

thanks.

Rod.