Hi

The old gdb system for vs 2015 was no longer needed when we discontinued support for vs2015. 

Today you just need to install Visual Micro. You should uninstall the old vmicro gdb extension and will see that it is no longer available (or required)

When you have the latest Visual Micro installed in vs2017 you simply need to follow our documentation which basically tells you to enable gdb using the new vMicro>Debugger menu options. Select "Hardware Debugging" then select your debugger such as EDBG. 

Does this help?

GDB in vs2015 will not work, furthermore there is a different install of vmicro in 2015 tools>extensions and updates. The release notes a year or two ago explained that older ide versions 2012-2015 need to uninstall vmicro and install again from the gallery. However that old version is not supported/updated so use vs2017 or 2019.