The blinking B and C lights indicate that the black and color cartridges are low. This has nothing to do with the wi-fi issue that you are experiencing. If the alarm light is also lit or flashing, please add a comment with that information.
For the wireless network issue, your best bet may be to reset the network settings to the factory default. Press the Maintenance button repeatedly until the LED screen shows a "t". Then press the Color or Black button. See https://www.canon.co.uk/support/consumer_products/pixma_printer_wireless_connection_setup/mg3250_printer_wireless_connection_setup/
; scroll down to see the reset information. After this step, if the network uses WPA or WPA2 security, press and hold the Maintenance button for approximately 5 seconds. The LED screen should show a bar at the bottom. Press the Fit to Page button. When the bar moves to the center and then the top, press the WPS button on the access point within two minutes. Wait for the unit either connect or show an error.
If your router is not set for WPA or WPA2 security protocol or the WPS button doesn't work, then you need to use a computer to redo the installation. First, install the setup software for the Pixma MG3250. If you do not have the install disk, it's available here: https://www.canon.co.uk/support/consumer_products/products/fax__multifunctionals/inkjet/pixma_mg_series/pixma_mg3250.aspx?type=software&language=&os=WINDOWS%2010%20(64-bit)
. Begin the installation and click on the button for Wireless Connection. Walk through the steps and press and hold the Maintenance button when you see the Connect to the Network screen. Press Next when the LED shows the bar at the bottom. Press Next again. Choose the Wireless Setup Using the USB Cable. Go through all of the steps and connect the USB cable when prompted to do so. Press Next and wait for the printer to be detected. After the printer is detected, confirm the Access Point that is shown. (Note: for the Mac OS, there are a few extra steps.) Unplug the USB cable when prompted to do so.
I hope this helps.