On 30th September 2021 OVMS modules posting to dexters-web.de V2 server will be unable to connect, see the post on dexters-web.de for more info: https://dexters-web.de/urgent-ssl-update-text_99.en.htm
The solution linked to by the dexters.web.de post involves manually uploading the certificate. An easier solution which has worked for me is to flash the latest 'edge' firmware which includes the certificate:
1. login to the ovms module
2. Select Config > Firmware then 'Flash from web' tab
3. Enter URL 'api.openvehicles.com/firmware/ota/v3.1/edge/ovms3.bin'
3. Select 'Flash Now'
4. Wait for firmware to download then reboot
OVMS should now be running 3.2.017 or later and V2 server will now connect to dexter-web.de