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Perhaps you simply need to go into the WiFi router box's
setup utility, and set the router into 2.4 GHz mode only. It may be a wireless-N-capable router, in which case, for it to work with your printer, you will need to set it to inhibit the maximum speed capability or 5 GHz capability, and only operate in the 2.4 GHz (Wireless-G) mode.
Does that sound likely to be the answer to your problem? if so, please try it, and tell me the result. Thanks.
(I regret that I am not able to offer Live Phone Call service at this time; However, your request is still open to other Experts in this category, and one of them may pick up on it at any time.)
Do you have a Windows PC? one that is hooked up to the router?
If so, I have a procedure for you to follow, to access and change that setting on your router.