Please see note from Siteground after I reported an issue

Please see note from Siteground after I reported an issue when trying to login.
Any input gratefully received.
Thanks, Jim.
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After further investigation and testing we were able to find the problem as it was caused by the plugin: "wpmudev-updates". We have now disabled the plugin by renaming the directory for it to "wpmudev-updates_disabled" and now the WordPress back-end is opening and working normally.