URL route and missing & request method problems

Error message on Emails and Subscribers List sections

No route was found matching the URL and request method.

I can no longer view all sent emails nor see the subscribers list – but it does correctly state the number of subscribers (87)
I am WP v7. PHP up to date. All plug-ins up to date. Theme (Exodus) up to date. All plugs in are automatically enabled for updates. I have re-saved all permalinks and run troubleshoot to check all plug-ins and themes. Have also run on a different browser but still the same issues.
I recreated a template yesterday and sent out an email and that has all processed. My normal process is to duplicate and then edit the prior week’s newsletter.
I use Send Grid to send out if that is relevant?
I can see the prior emails by copying the details on to a separate page but why has this changed?

This issue started after 24th May and before 31st May – the email I sent out on 24th was usual process. These issues arose on the 31st – I am fairly sure that was before the latest update? I have been waiting to see if further updates cured the issue but a week later still a problem.