WNDR 3400v3 cannot find the server to allow sign in to my bank account

WNDR 3400v3 with latest firmware running with MAC with most recent OS. Everything works great except for one website, my credit union. I can open the website and navigate freely until I try to sign in to my account. Won't work, says Safari cannot establish a secure connection. All other websites can be accessed via secure sign ins. The credit union says they have no known issues. My ISP says its probably the router. That appears to be correct because if i bypass the router I can sign in. I can also sign in on my phone if i disable the WIFI. Any ideas on settings within the router that I can change to fix this issue?