I bought a pro version, it worked for a couple days and stopped, now I cannot download anything and complained to them by email but no respond from them.

Does it still have 'Pro' next to the logo, top left?

If not, I guess it's become deactivated.

Try re-registering it again using the account icon top right.

Make sure you use the e-mail address that you registered it originally with.

You should get an e-mail to click on a link to re-register it.

HTH.