If you upgraded to Android 4.2 Jelly Bean, you may have run into an issue where your SwiftKey keyboard has disappeared. It may be completely gone or simply disabled. SwiftKey is aware of the issue and is working with Google on a resolution:
This is a rare but unfortunate report that we’ve recently been made aware of. We have contacted the Android development team to understand what caused this in their code. We are doing what we can on our end to resolve this issue for those affected.
While SwiftKey works on a permanent fix, there is a fairly simple fix: Redownloading and reinstalling SwiftKey. Be sure to download it using the same account and store you bought it from originally to avoid being charged a second time.
It does not affect everyone – Gadgetorama’s own Nexus 7 did not exhibit this behaviour either during the 4.2 or the 4.2.1 upgrades.
Read more: SwiftKey