I can not open solution with my project. On 5.4 prev. 9 was ok. Output window shows:
D:\MbedDemo\MbedDemo.vcxproj : error : Unable to read the project file "MbedDemo.vcxproj".
C:\Program Files (x86)\Sysprogs\VisualGDB\MSBuild\SysprogsPlatform.targets(164,71): The attribute "ItemType" in element <ToolchainSettingsContainer> is unrecognized.
No problem, we can help you. Please share a screenshot of your Help->About VisualGDB window and a screenshot of the exact error message you get and we will look into this.