Hi,
You mentioned that you had rebooted the router, and the iPhone. Any change if you try the following procedure (in the exact order) instead?
Power off the Wi-Fi router, the printer, the iPhone, and all other devices/computers. Wait two to three minutes. Power on the router. Wait two to three minutes. Power on the printer. Wait a minute or two. Power on the iPhone. Finally, power on all other devices/computers.
Modern dual-band routers with automatic device detection and band selection have been reported to cause difficulties in some cases. If so, a manual setting or renamed network may be needed.
If necessary, please post back with the exact router model (do not post any serial numbers or access codes). Also, please let us know which Epson printer model you are using.