It sounds like you're trying to update firmware from an end-user perspective. With the way DOCSIS works, the provider (Cox) controls the firmware version on the modem by setting it during the bootup process. There's no easy way for an end-user to upgrade their own firmware. If you're having issues, I suggest taking a look at your RF levels. If you go to http://192.168.100.1 you might see a diagnostic page for the modem, and on one of the tabs there should be signals or levels. You want to make sure your downstream levels are between -10 to +10 on all of the channels, and transmit levels between roughly 33 and 49. You can check this both in the day and nighttime hours (or whenever you have issues) to make sure they're still within range. If they're not, contact Cox for a service call and/or check your cabling.
It sounds like you're trying to update firmware from an end-user perspective. With the way DOCSIS works, the provider (Cox) controls the firmware version on the modem by setting it during the bootup process. There's no easy way for an end-user to upgrade their own firmware. If you're having issues, I suggest taking a look at your RF levels. If you go to http://192.168.100.1 you might see a diagnostic page for the modem, and on one of the tabs there should be signals or levels. You want to make sure your downstream levels are between -10 to +10 on all of the channels, and transmit levels between roughly 33 and 49. You can check this both in the day and nighttime hours (or whenever you have issues) to make sure they're still within range. If they're not, contact Cox for a service call and/or check your cabling.