Hi, my name is Jose, a Windows user like you. I'll be glad to help you today. I'm sorry to hear this.
Please consider that your phone does not recognize Microsoft authentication for shared folder access. The Elise's suggestion is to identify the local user for your Microsoft account. Please select start, type CMD and choose it. When CMD open you will see something like C:\Users<myuser>
Use this folder name as username to access the shared folder from your phone.
Please let me know if you need any further assistance.