I purchased TouchDown for Android from the Google Play Store but did not receive a key
Sorry about that, the digital key setup can be a bit confusing. When you purchase a license from the Google Play Store, you don’t need or get a serial number. The Key application you purchase contains the serial number inside it. To license the main TouchDown application, please download and install the Exchange by TouchDown Key application, then open the Exchange by TouchDown Key app at least once on the device. As long as you have that application installed on the device, your main TouchDown application will remain licensed.
If you downloaded some time ago but never installed, you can find the download in the Play Store application by clicking on “my downloads” to resume the installation process. You can be sure the key is installed by going to the app menu and looking for Exchange by TouchDown Key (it will have an icon with keys on it). Tap that icon to open the key app once and you should be able to return to use the main program.
Please note: if your free trial expired before you purchased a key, then TouchDown went into free mode and shut off a few services. You will need to go to settings within TouchDown and run the quick configuration wizard to completion in order to reset your connection to the server and get back to using TouchDown fully featured.