Hello,
Check for latest updates at Settings > Update & Recovery > Windows Update, see if V2004 is offered.
Else, refer this page to learn about known issue with V2004: https://learn.microsoft.com/en-us/windows/release-information/status-windows-10-2004. Check if any of known issue relates to you.
If no issue is related to you, upgrade to V2004 via ISO file.
Refer this step-by-step guide:
https://www.kapilarya.com/how-to-upgrade-to-windows-10-using-iso-file
Let us know if this helps!
Note: Included link in this reply refers to blog post by a trusted Microsoft MVP.