I deleted my gmail and can't add it back again

My gmail account in Thunderbird stopped working on my lap top but is is still working on my phone and note pad. This happens from time to time so I usually just delete the account in Settings then Account settings then just add it as a new account. But having deleted the account I now can't add it back again. It doesn't allow me to add the account. At the Incomming Server settings Error Creating Account Incoming server already exists