I solved this in my case earlier
If anyone else has this problem here’s my solution. On a corporate network behind Zscaler.
After adding your proxy settings in environment variables PIO installed successfully but failed due to the above certificate error. Max retries exceeded with url: /v3/packages/platformio/tool/contrib-piohome (Caused by SSLError(SSLCertVerificationError(1, ‘[SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed: unable to get local issuer certificate (_ssl.c:1125)’)))
In VS Code File>Preferences>Settings search for ssl, Application>Proxy Uncheck Proxy Strict SSL. Now PIO home loads successfully. Hope this helps!