Sagemaker Studio Notebook: Failed to start kernel and Error listing projects. Error message: undefined. Args: "Missing credentials in config, if using AWS_CONFIG_FILE, set AWS_SDK_LOAD_CONFIG=1"

I have an issue with Sagemaker Studio: I can not see my projects, pipelines, nor work with Notebooks. So, I have been working with Sagemaker for more than 1 year, and never faced an issue like this before. Three days ago, everything worked as it should, I executed many pipelines, worked on my notebook, and now nothing works. When I open Sagemaker Studio, and when I click on Sagemaker Resources->Projects, the following error is displayed: Also, If I want to see my pipelines, this is the error that is displayed: And if I want to work on some of my notebooks there, here is the error that I got for any kernel that I choose (the ones that are provided from AWS): I never used local mode, I just worked on AWS Sagemaker Studio Project and that's it. My account has Access Key and Access Secret and it is activated. What can be an issue? Is it something related to a config file? If yes, where can I find that AWS_CONFIG_FILE? (Note: Also, I have never used AWS CLI, because I never needed it, is this an issue that can be fixed only through AWS CLI?)