My data is also no longer going to WU. It was fine for years with the Hub. I bought and installed the Access device. Data is correct and up to date in my Acurite dashboard (with either connection) but still none flowing to WU. I went back and forth several times between the two without any change. I tend to think the issue is with Acurite servers.
You should not have a problem using the smartHUB to send to Weather Underground. Please remove your Weather Underground credentials from My AcuRite completely and re-add them. Please DO NOT COPY AND PASTE THE CREDENTIALS. Use your Station Key as the password instead of your password for Weather Underground. Let us know if this issue continues. Thank you.