PlusOne router and Macbook

[#1]

Just the other day my macbook refuses to connect with our PlusOne via wifi, it is saying invalid password.
All other macs, phones, tablets work fine. Any thoughts?
I've tried a restart of macbook.

[#2]

try splitting the 2.4 and 5GHz networks, that helped with our MBP that sorted our issue out.

[#3]

Not sure what you mean....do you mean disable one of them? I am certain the MB is old and its 2.4.

[#4]

In advance wireless settings change the ssid of one of them. I just added a 5 on to the end of the 5ghz one.
We had issues with a 2009 MBP, which is quite old.

[#5]

@dvorak  is your ipv6 fix relevant here?

[#6]

shouldn't be - that's more to do with the hub zero and it crashing the MBP.
though I haven't tried switching IPv6 on again.