Qt VS Tools: error reading VS project settings

To solve your problem, you need to remove the QTDIR and QMAKESPEC environment variables that remain in Windows after installing older versions of Qt.

Encountered the exact same problem and the only solution I have found was reverting to an older version of the Qt Visual Studio Tools extension.

Visual Studio has been painfully persistent about updating the version even once I installed an older one, so make sure to disable automatic extension updates (Extensions → Manage Extensions → Extension Settings → Uncheck Automatically search for updates/Automatically update extensions).

Hope it helps.

For any future readers who have this problem, start your maintenance tool or Qt installer, e.g. C:\Qt\MaintenanceTool.exe, "Add or remove components", and then make sure Qt/<version>/MSVC is installed, as shown in the image below:

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Then you'll be able to select that Qt version instead of MinGW, since the Visual Studio extension only supports the MSVC compiler and not MinGW.