why would they eventually come back? it's unlikely, unless there is a problem with both of them and then it get's fixed which is very unlikely.
the above comment makes sense, but it's also not as bad as it may sound, the problem could be this
- your VPN server itself is blocking slush and kano pool servers for some reason.
you got two things to try to for now:
1- change the VPN server location , until you get those pools back, try to chose a country that is crypto friendly.
2- change the DNS on your router / miner, use a public dns like google's 8.8.8.8
* step 2 is not recommended if you are using online wallets
also you probably have to reboot the miner for a dead pool to become alive again, there is no guarantee that cgminer is going to ping the pool aside from the start-up period.
but you don't have to do this at every change you make, you can simply try pining those pools from a pc that runs on the same network and using the same vpn by:
1- open CMD
2-type
ping kano.is
if you get something like this
then your miner will find the pool "alive"
however if you get something like this
then your miner will show pool "dead".
post back your findings, there are a few more things to try out. but these are the most 2 common solutions i can think of now.