Router not being 'recognised'

I received a Netgear C6300BD router from my ISP in August of this year. On a laptop I run Bitdefender 2017 AV and when I do  a 'vulnerability scan' it provides a warning..."Router : Password strength: No password...your router is unsecured....change router password" (I'm also provided with a MAC address). I've changed the Admin router password from its default 'password' on numerous occassions to one that is 26 characters long and I still get the same warning message. I contacted Bitdefender and they basically said "...it's a router problem..not us...BUT due to the length of your password there is liittle chance of a brute-force attack and due to the limitations of your router you should be fine".

On another computer my Avast! AV also experiences problems identifying the Netgear router....both Bitdefender and Avast! iidentify the same MAC address as being the problem. 

I've googled till I can google no more in an attempt to resolve this issue but my computer knowledge is horrible so most of it now goes over my head.

Any explanation as to what I can do to make the router 'recognised' would be appreciated (in terms that a 5yr old would understand please...no offense to 5yolds). This is a stupid question but, due to the long router password and the fact that everything seems to be going well, is this a serious problem? (I may be in denial)