Why my UE 5.6 asks for rebuilding when i check the Always load last project on startup checkbox?

There are these folders/files in my project directory: .vs, Binaries, Config Content, DerivedDataCache, Intermediate, Saved, Source, “.editorconfig”, “.vsconfig”, “Pong.sln”, “Pong.uproject”, “shadertoolsonfig.json”. The names with quotes are files. I’ve removed the Source folder, and it still asks for rebuilding, and after clicking yes, it says the same things. It still only opens when the project auto opens at the start of the UE5.6 editor.
In the .uproject file, there was a Visual Studio Integration Tool plugin, so I removed it without success. The rest of the file looks like this:
{
“FileVersion”: 3,
“EngineAssociation”: “5.6”,
“Category”: “”,
“Description”: “”,
“Modules”: [
{
“Name”: “Pong”,
“Type”: “Runtime”,
“LoadingPhase”: “Default”
}
],
“Plugins”: [
{
“Name”: “ModelingToolsEditorMode”,
“Enabled”: true
},
]
}