Generally, when a network adapter that used to work properly no longer appears in Device Manager, the reason is one of two things: the device has been turned off (i.e., the computer is in "airplane mode") or the device has failed.
- What is the make and specific model of your computer?
- Please list the complete names of all items in the "Network adapters" section of Device Manager, and note if any has a warning icon
- If there is an "Other devices" section in Device Manger, please list the complete names of all items in this section
An update to Windows Defender (which will be shown in your "Update History" as "Security Intelligence Update for Windows Defender Antivirus - KB915597 (Version 1.xxx.yyy.0)") will have no effect on your network adapter.
If you have (or had) both an Ethernet network adapter and a wireless network adapter and one of them is the one that no longer appears in Device Manager, if the other is still showing in Device Manager, can you connect to your router with that adapter? That is, assuming that it was your wifi adapter that disappeared, can you access the Internet if you connect your computer to your router with an Ethernet cable?
Its happened many times before. I cant remember how i fixed it last time just that it was something to do with windows defender. Which i noticed had been updated.
What happened many times before? Updates having to do with Windows Defender or your network adapter stopping to work? Windows Defender signature updates are quite frequent.
Services shows that diagnostic system host is stopped and cannot be started as the option is greyed out. The other 2 say they are started.
I assume that "the other 2" are the Diagnostic Service Host and either the Diagnostic Policy Service or the Diagnostics Tracking Service. These observations may be relevant to why "Troubleshooting can't continue," but they are not relevant to why your network adapter isn't working. I've never found the "troubleshooting" software in Windows 7 to be particularly helpful.