OmniSharp returning System.IO.FileNotFoundException

I'm trying to get auto-completion with Unity, and I keep getting this message:

Starting OmniSharp server at 12/28/2021, 4:12:57 AM
    Target: d:\UnityHub\Igor\Igor.sln

OmniSharp server started.
    Path: c:\Users\james\.vscode\extensions\ms-dotnettools.csharp-1.23.17\.omnisharp\1.37.17\OmniSharp.exe
    PID: 21752

[info]: OmniSharp.Stdio.Host
        Starting OmniSharp on Windows 6.2.9200.0 (x64)
[info]: OmniSharp.Services.DotNetCliService
        Checking the 'DOTNET_ROOT' environment variable to find a .NET SDK
[info]: OmniSharp.Services.DotNetCliService
        Using the 'dotnet' on the PATH.
[info]: OmniSharp.Services.DotNetCliService
        DotNetPath set to dotnet
System.IO.FileNotFoundException: C:\Program Files (x86)\Microsoft Visual Studio\2017\Community\MSBuild\15.0\Bin\Microsoft.Build.dll
   at System.Diagnostics.FileVersionInfo.GetVersionInfo(String fileName)
   at OmniSharp.MSBuild.Discovery.MSBuildInstanceProvider.GetMSBuildVersion(String microsoftBuildPath) in D:\a\1\s\src\OmniSharp.Host\MSBuild\Discovery\MSBuildInstanceProvider.cs:line 104
   at OmniSharp.MSBuild.Discovery.Providers.MicrosoftBuildLocatorInstanceProvider.<>c.<GetInstances>b__1_0(VisualStudioInstance instance) in D:\a\1\s\src\OmniSharp.Host\MSBuild\Discovery\Providers\MicrosoftBuildLocatorInstanceProvider.cs:line 30
   at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
   at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
   at System.Linq.Enumerable.ToArray[TSource](IEnumerable`1 source)
   at System.Collections.Immutable.ImmutableArray.CreateRange[T](IEnumerable`1 items)
   at OmniSharp.MSBuild.Discovery.MSBuildLocator.GetInstances() in D:\a\1\s\src\OmniSharp.Host\MSBuild\Discovery\MSBuildLocator.cs:line 115
   at OmniSharp.MSBuild.Discovery.Extensions.GetBestInstance(IMSBuildLocator msbuildLocator, Version minimumMSBuildVersion, ILogger logger, Boolean& invalidVSFound, Boolean& vsWithoutSdkResolver) in D:\a\1\s\src\OmniSharp.Host\MSBuild\Discovery\Extensions.cs:line 109
   at OmniSharp.MSBuild.Discovery.Extensions.RegisterDefaultInstance(IMSBuildLocator msbuildLocator, ILogger logger, DotNetInfo dotNetInfo) in D:\a\1\s\src\OmniSharp.Host\MSBuild\Discovery\Extensions.cs:line 17
   at OmniSharp.CompositionHostBuilder.Build(String workingDirectory) in D:\a\1\s\src\OmniSharp.Host\CompositionHostBuilder.cs:line 71
   at OmniSharp.Stdio.Host..ctor(TextReader input, ISharedTextWriter writer, IOmniSharpEnvironment environment, IServiceProvider serviceProvider, CompositionHostBuilder compositionHostBuilder, ILoggerFactory loggerFactory, CancellationTokenSource cancellationTokenSource) in D:\a\1\s\src\OmniSharp.Stdio\Host.cs:line 49
   at OmniSharp.Stdio.Driver.Program.<>c__DisplayClass0_1.<Main>b__1() in D:\a\1\s\src\OmniSharp.Stdio.Driver\Program.cs:line 74
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.<>c__DisplayClass146_0.<OnExecute>b__0(CancellationToken _)
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.<ExecuteAsync>d__157.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
   at System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
   at McMaster.Extensions.CommandLineUtils.CommandLineApplication.Execute(String[] args)
   at OmniSharp.HostHelpers.Start(Func`1 action) in D:\a\1\s\src\OmniSharp.Host\HostHelpers.cs:line 29

I'm not really sure what's going on, but I installed Visual Studio as well and that also failed as a solution.