Method not found: 'Void Newtonsoft.Json.JsonSerializerSettings..ctor(Newtonsoft.Json.JsonSerializer"

Run this PowerShell command and it will fix the issue.

# -----------------------------

# Install Newtonsoft.Json 13.0.3 to GAC (keep old versions)

# -----------------------------

# Temp folder for download

$tempBase = "C:\Temp\NewtonsoftInstall"

New-Item -ItemType Directory -Force -Path $tempBase | Out-Null

# Target version

$version = "13.0.3"

$publicKeyToken = "30ad4fe6b2a6aeed"

# NuGet package URL

$nugetUrl = "https://www.nuget.org/api/v2/package/Newtonsoft.Json/$version"

# Folder for this download

$tempPath = Join-Path $tempBase "Newtonsoft_$version"

New-Item -ItemType Directory -Force -Path $tempPath | Out-Null

# Download NuGet package

$nupkgPath = Join-Path $tempPath "newtonsoft.nupkg"

Invoke-WebRequest -Uri $nugetUrl -OutFile $nupkgPath

# Rename .nupkg to .zip for extraction

$zipPath = Join-Path $tempPath "newtonsoft.zip"

Rename-Item -Path $nupkgPath -NewName "newtonsoft.zip"

# Extract ZIP

Expand-Archive -Path $zipPath -DestinationPath $tempPath -Force

# Locate net45 DLL

$dllPath = Get-ChildItem -Path $tempPath -Recurse -Filter "Newtonsoft.Json.dll" |

Where-Object { $_.FullName -match "\\net45\\" } |

Select-Object -First 1

if (-not $dllPath) { throw "ERROR: Newtonsoft.Json.dll not found!" }

# GAC path for this version

$gacRoot = "C:\Windows\Microsoft.NET\assembly\GAC_MSIL\Newtonsoft.Json"

$gacFolder = "$gacRoot\$version`__$publicKeyToken"

# Skip if this exact version is already installed

if (Test-Path $gacFolder) {

Write-Host "Newtonsoft.Json version $version already exists in GAC."

return

}

# Create GAC folder

New-Item -ItemType Directory -Path $gacFolder -Force | Out-Null

# Take ownership & set permissions

takeown /f $gacFolder /r /d y | Out-Null

icacls $gacFolder /grant administrators:F /t | Out-Null

# Copy DLL into GAC

Copy-Item $dllPath.FullName -Destination $gacFolder -Force

Write-Host "Installed Newtonsoft.Json version $version into GAC."

Write-Host "Location: $gacFolder"