Welcome!What Hardware version is your router and DAP? Look at sticker under router and DAP.
What
Firmware version is currently loaded? Found on routers web page under status.
What region are you located?
Some things to try:
Turn off Advanced DNS Services if you have this option under Setup/Internet/Manual.
Turn on DNS Relay under Setup/Networking.
Setup DHCP reserved IP addresses for all devices ON the router. Setup/Networking
Ensure devices are set to auto obtain an IP address.
Set Firewall settings to Endpoint Independent for TCP and UDP under Advanced/Firewall.
Enable uPnP and Multi-cast Streaming under Advanced/Networking.Wireless Installation ConsiderationsWhat wireless modes are you using? Under Setup/Wireless/Manual.
Try single mode G or N or mixed G and N on the 655 router?
Turn off WISH, and WPS under Advanced.
Turn off Short GI, WLAN Partition,and Extra Wireless Protection if you have it. Under Advanced/Advanced Wireless.
Turn off all anti virus and firewall programs on PC while testing. 3rd party firewalls are not generally needed when using routers as they are effective on blocking malicious inbound traffic.
Turn off all devices accept for one wired PC while testing.