I have the same issue as you with the 2.4 Ghz. The 5.0 Ghz is working fine. I have reported this issue a total of 5 times over the last 3 weeks. I am currently using the service provider's router.
Please provide more details about your exact issue.
Have you first tried powercycling / re-starting the device ? No joy ? Try hard resetting the device by pressing and holding in the recessed reset button on the rear for 30 seconds. You will lose any customized settings.