Yes, I have tried deactivating plugins.
Since deactivating my plugins, I now cannot use Jetpack after reactivation. It says my site is inaccessible.
I have also contacted my webhost who cannot provide me with an answer.
I gave all of those things a go (deactivated all plug-ins, switched to the Twenty Fifteen theme) and it still told me my feed was not valid?
Does this take a while to update, I only tried this for a few minutes?
Otherwise I’m really not sure what my issue is.