"I can change the frequency from 2.4 to 5gz ...................but laptop flatly refuses to even see the network."
It's still unusual to find laptops with "dual band" adapters in them - even current models. So that almost certainly explains why your Toshiba can't see any 5GHZ wireless networks. However, lots of Mac models have had them for quite a while so that explains why those devices can connect without problem.
There are two workarounds for you. If your router supports it, enable 2.4GHZ and 5GHZ. That'll give you two discrete networks - a 2.4GHZ one for your Tosh and a 5GHZ one for your Mac devices. Or, you can buy a USB dual-band wireless adapter for your laptop.
If you want confirmation of your Toshiba's capabilities, post the full model number and I'll check out its specifications.