HI @mjaghlassianRF4AJ ,
This could be one of a couple of things. If you upload a file through the web interface and then try and open through Revit it does not allow you. It wont see the file no matter which version. You can get around this by going through the Desktop Connector.
The next is the model is saved in another version and which you need to make sure you are using the correct version. ie. saved in Revit 2020 but you are trying to open with Revit 2021. It doesn't see the file.
Oh another are the workshared models and you don't have access to workshared models?
Here are some articles on Autodesk Knowledge Network
Cannot access BIM 360 projects in Revit
Some BIM 360 models or folders are not displayed on open or during collaboration in Revit
Please click the Accept Solution button if my reply answers your question.
Twitter: @TheDarkAsset
LinkedIn: gareth-spencer-84202532
Gareth Spencer
BIM Technical Consultant | Man and Machine (UK)