Try updating the router’s firmware and disable uAPSD in the wireless adapter properties.
What type of security encryption is being used?
Can you connect to other DHCP networks with the Intel® wireless adapter?
Are other systems connecting properly to this wireless adapter?
Both, laptop and router is fully updated.
I changed uAPSD and I will be testing.
Security encryption does not matter, because I also tried with open network.
I cannot connect neither at home, work, my iphone hotspot or mobile modem/router.
My old Lenovo x220 and every other system connect my WIFI without any problems.
Only new x240 with 7260 has problems. Works only with static IP.
Try resetting the tcp/ip stack. Otherwise, I would think something is interfering with the connection, like security software. You may also try in safe mode with networking.