1.000.000 $ question

I've a dual band wireless AP 2.4 and 5 GHz
The printer is connected trough 2.4 Net, the PC(1) on 5GHz

If I connect an other PC(2) and I ping PC(1) and vice-versa it works wonderfully
If I connect PC(1) on 2.4GHz and I print on MX535 (cups dnssd://Canon%20MX530%20series._ipp._tcp.local/) it works

If I connect PC(1) on 5GHz and I print on MX535 (cups dnssd://Canon%20MX530%20series._ipp._tcp.local/) it NOT works

CUPS 1.7.5
DEBIAN 8.4
cnijfilter-mx530series-4.10-1-deb

You should provide router make/model details since that is likely the relevant factor here. Perhaps the dual-band router is isolating the two wireless networks. Check the router configuration for options such as AP isolation and UPnP.

At the beginning I thought the same... and I try successfully to connect (ssh) and ping PC(1) and PC(2).

Anyway the AP is a D-Link GO-DSL-AC750
the option "isolate clients" is set to OFF in both 2.4 and 5GHz networks. In guests' is set to ON (but nobody is connected to guests networks). UPnP is OFF due to its insecure nature.

Suggestions?
Known bugs?

nmap ?

You're using Avahi/Bonjour for printer discovery. I suspect the discovery is being blocked. You could use avahi-browse (Debian avhi-utils package?) like this to discover Avahi devices
That will help with the diagnosis.

Alternatively, use the cnijnet backend provided by the Canon driver. You may need to configure manually via the CUPS web interface. Configure as if using the AppSocket backend, then edit manually. You can specify a MAC address or an IP address (if printer is already configured with a suitable static IP address)

For example, the URI might look like
These might be helpful to you

http://askubuntu.com/questions/75887...etwork-printer
http://linux.wikia.com/wiki/Getting_..._work_on_Linux

BTW, you could run the cnijnet backend manually like this to check that printer is detected as expected
This will do similar
Ports 8611-8614 are used for canon network printing, so check that your firewall is not blocking these.