MailPoet won’t let me edit my email text

Hi,

I've been using MailPoet for a while now without any issues. I create an email from a template every month informing my subscribers what is coming up this month. This month, I can't edit the text in the email created from the template. I can highlight it, but not change it. The system only allows me to move the block around. If I add a new text block the same thing happens, I've tried creating an email from scratch with the same result,

In previous months I just created a new email from a template and changed the text.

Any ideas please ? Thanks in advance for any help you can offer.