My Win 7 PC won't connect to eero router

Have just had full fibre and eero (thru' TalkTalk) fitted.
Tablets and phones all connected automatically and work well.
My two Win 7 PC's will not and cannot "see" the available network, so I cannot connect.
TalkTalk community and eero legacy dept have suggested remedies. I have tried them all, several times (in case I misunderstood them), to no effect. The eero legacy dept signed off its last email with, "Kindly inform us of any updates you may have."
I am bemused.
My PC has a Realtek RTL881AU wireless adapter. (802.11ac)
Can anyone answer the following questions please.
1) Can I replace the RTL8811AU card with aRTL8852BE card on my motherboard?
2) Will a USB wifi dongle for Win 7 PC's do the same job. (802.11ax)
Hope you can help, John

John,

check the security settings on the wifi card... security are they WPA2

Many thanks, but I done that and I've used the troubleshooting feature as well.
I know my Realtek wireless adapter card is old, as it came attached to the motherboard. I know :-
1) that the card has "fully up to date drivers", but it cannot handle wi-fi 6. The card is 10 years old and its drivers are that age too, hence every time I try to update them, it comes back with "Your drivers are the latest version".
2) eero says its router can connect to Win 7 PC's, but it doesn't
3) eero says it does not "hide" its router from the list of routers that are available in the neighbourhood, so where is it?

It seems to me that the R&D and Legacy depts. of eero are not commmunicating and the glitch in its excellent system has not been found, until an old codger like me refuses to give up a perfectly good OS and computer, which is old. They are probably only considering 5 year old computer systems for their "legacy" connections.
This is why I asked the questions about renewing adapter card and wi-fi dongles.
Thanks for taking the ttime to help me.