Danified

I have taken over the role of managing SCCM in an existing setup. I have over 2000 devices with the client installed and I have 242 that do not according to SCCM. Some of these devices do indeed have SCCM installed and some don't. From looking at the logs it looks like I have a certificate issue but I don't understand it well enough to know how to fix it. I am getting: Unable to find any Certificate based on Certificate Issuers Failed to receive ccm message response. Status code = 403 ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) GetDPLocations failed with error 0x80004005 ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) Failed to get DP locations as the expected version from MP 'HTTPS://<ServerNameRemoved>'. Error 0x80004005 ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) Failed to find DP locations from MP 'HTTPS://<ServerNameRemoved>' with error 0x80004005, status code 403. Check next MP. ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) Only one MP HTTPS://<ServerNameRemoved> is specified. Use it. ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) Have already tried all MPs. Couldn't find DP locations. ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) GET 'HTTPS://<ServerNameRemoved>/CCM_Client/ccmsetup.cab' ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) Failed to successfully complete WinHttp request. (StatusCode at WinHttpQueryHeaders: 403) ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64) DownloadFileByWinHTTP failed with error 0x80004005 ccmsetup 5/12/2016 9:38:41 AM 3172 (0x0C64)