If you cannot reliably receive calls and/or place Google Voice calls, enable NAT Keep Alive and properly set its interval (115 or 55 seconds). Other than that, don't enable any NAT related options, because KoT handles NAT like nobody else.
In most cases, you only need to fill in three parameters:
proxy server: sip.kots.us (port 5060; or 5062, 5061 for more codec support than G729)
user name: the 11-digit line # (not the master # that ends with 0, nor your account name)
password: the password for the line (not the one for your account).
Change 5060 to 5062 in following examples, if you want more codec support than G729.
Replace "5557778888" with the phone # that you want to reach when someone dial 911 and replace "555" with your area code. (warning: KoT VOIP does not support emergency calls!)
Then copy and paste above line into the Dial Plan field and make changes to all the red fields in the following photos.
If you have a PAP2 and its variants, you must correct "RTP Packet Size" to 0.020 and "G729 Codec Name" to G729 (w/o a), respectively, see red circles below. Otherwise, you can only use G729 and the 5060/5080 pair.
If you have Auto Provisioning enabled, you must do its configuration in your OBIHAI account in OBIHAI website. If you do its configuration directly as showing below, you must first disable Auto Provisioning.