After an upgrade from 4.4.0-131-generic to 4.4.0-133-generic (Ubuntu 16.04) the wireless connection did not work. Also no wireless options such as "Enable Wi-Fi" were showing in the task bar or menu. Wireless worked fine with 4.4.0-131-generic.

The wireless in my computer uses the rt2800pci module. Trying to load the module with modprobe resulted in a module not found error. With some more investigations it turned out some files in the directory /lib/modules/4.4.0-133-generic/ such as modules.builtin and modules.builtin.bin had zero length. I would consider this an incomplete installation and decided to reinstall the update package.

After a reboot starting 4.4.0-131-generic i used following commands for the reinstall:

sudo apt-get update sudo apt-get --reinstall install linux-image-4.4.0-133-generic

Then rebooted using 4.4.0-133-generic and found the wireless connection working. The files in the /lib/modules/4.4.0-133-generic/ directory now all had a non-zero length.

The reinstall of the update package solved the wireless connection errors for me.