when you assign static addresses you need to have a range of numbers reserved, ie not available to DHCP for its use. An easy way to do that is to go into the router configuration under the DHCP section and where it gives you the option to pick a starting address and either ending address or # of users, pick a starting address of something like 192.168.1.21 and an ending address of 192.168.1.50 ( it may only give the option for max users - pick 30 for this example)
Then assign, at the epson printer, to 1) not use DHCP , 2) manual configure the TCP/IP address to 192.168.1.100 (outside the range that DHCP will use, don't pick a number higher than x.x.x.239 or lower than x.x.x.5 to stay away from internal addresses used by the router and wireless) for example, and enter the default gateway address of 192.168.1.1, subnet mask of 255.255.255.0 in the printers network configuration page.
Then reinstall the epson driver. you should be good to go.
What was described before about not being able to locate the printer is what i would expect from a changing ip address. The windows drivers assign a port using that address during printer discovery, so when the tcp/ip address changes the driver would not be able to locate it. It is likely that the epson status software is not using tcp/ip to talk with the printer, so that is why it works. it probably queries the network using a different protocol, and finds the printer each time.
Unmanaged consumer level switches are usually transparent to the network unless you have set up a Virtual LAN or other static routing.