Microsoft acknowledged a new bug that has been introduced for some users on Windows 10 May 2020 Update (version 2004) that falsely reporting the internet connection status in the Windows Taskbar icon (Network Connectivity Status Indicator, NCSI).
At present, Microsoft has no solution for it as the issue is being investigated by the engineers at Redmond. If you are facing this issue, it's just a matter of time until a new fix comes up.
The new issue reportedly popping up on Windows 10 users upgraded to May 2020 Update (version 2004). According to Microsoft, the NCSI (Network Connectivity Status Indicator) icon on the Taskbar may report a "no internet" connection on Windows 10 devices that DO have internet access.
On the Technet Forum, Microsoft explains the issue as below:
Symptom:
Customers are reporting "no internet" access in the Network Connectivity Status Indicator (NCSI) on Windows 10 2004 devices that in fact can ping internet resources or browse web sites with internet browsers.
Current situation:
Microsoft has known about this issue but haven’t resolved it yet.
It is being investigated by Microsoft currently.