We moved to WPEngine from another hosting service last week. Things went well in staging and production after repointing the DNS on Wednesday through Friday. On Monday Zotero stopped working and there is a fatal error message in the logs which looks like this:

PHP Fatal error: Uncaught Exception: Invalid HTTP response version: 2 in /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/libZotero/build/libZoteroSingle.php:700#012Stack trace:#012#0 /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/libZotero/build/libZoteroSingle.php(1193): libZotero_Http_Response->__construct(200, Array, '<?xml version="...', '2', false)#012#1 /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/libZotero/build/libZoteroSingle.php(2392): libZotero_Http_Response::fromString('HTTP/2 200 \r\nda...')#012#2 /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/libZotero/build/libZoteroSingle.php(2719): Zotero_Library->_request('https://api.zot...')#012#3 /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/zotero-test.php(143): Zotero_Library->fetchCollections(Array)#012#4 /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/zotero-test.php(185): Zotero_Test->print_collection('WHKJ7FQA')#012#5 /nas/content/live/cthmultisite/wp-content/plugins/cthistory/templates/single.php in /nas/content/live/cthmultisite/wp-content/plugins/Zotero-Test/libZotero/build/libZoteroSingle.php on line 700

I've been in touch with WPEngine and they've reinstalled WPCore to see if that would resolve it and also excluded this plugin from the network cache. This has not resolved the issue.

I have no idea what any of this means or how to fix it, but welcome any insights anyone might have.

Thanking you in advance.