MSBuild does nothing

For one of my solutions, nothings happens when I ask Rider to build (see below).

Other solutions work fine in Rider, and this solution builds as expected in Visual Studio and on the command line.

Deleting .idea folder and reopening makes no difference. What could be wrong???

Use build tool: C:\Program Files (x86)\Microsoft Visual Studio\2019\Enterprise\MSBuild\Current\Bin\MSBuild.exe
CONSOLE: Microsoft (R) Build Engine version 16.9.0+57a23d249 for .NET Framework
CONSOLE: Copyright (C) Microsoft Corporation. All rights reserved.
CONSOLE: Build started 2021-03-28 12:58:50.
Build completed in 00:00:00.664
Build succeeded at 12:58:50