Even though you normally are fine over wireless, that can change at any time. That's just the nature of wireless as it's very susceptible to interference from other devices, walls, floors, etc. You also may just need to power cycle your equipment. To do that, unplug your modem/router. Also, shut down your PC. After 2 minutes plug in the modem and router. Let them come back online completely. Start up your PC and try playing again.
It would be good to check your router for a firmware update as well.
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