Some pages are not displaying. It displays 500 error code

/var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Client.php(162): GuzzleHttp\Client->transfer()
16 #12 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Client.php(182): GuzzleHttp\Client->requestAsync()
17 #13 /var/www/public_html/lib/pkp/classes/plugins/PluginGalleryDAO.inc.php(59): GuzzleHttp\Client->request()
18 #14 /var/www/public_html/lib/pkp/classes/plugins/PluginGalleryDAO.inc.php(32): PluginGalleryDAO->_getDocument()
19 #15 /var/www/public_html/lib/pkp/controllers/grid/plugins/PluginGalleryGridHandler.inc.php(127): PluginGalleryDAO->getNewest
Compatible()
20 #16 /var/www/public_html/lib/pkp/classes/controllers/grid/GridHandler.inc.php(314): PluginGalleryGridHandler->loadData()
21 #17 /var/www/public_html/lib/pkp/classes/controllers/grid/GridHandler.inc.php(1032): GridHandler->getGridDataElements()
22 #18 /var/www/public_html/lib/pkp/classes/controllers/grid/GridHandler.inc.php(923): GridHandler->renderGridBodyPartsInternal
ly()
23 #19 /var/www/public_html/lib/pkp/classes/controllers/grid/GridHandler.inc.php(643): GridHandler->doSpecificFetchGridActions(
)
24 #20 /var/www/public_html/lib/pkp/classes/core/PKPRouter.inc.php(397): GridHandler->fetchGrid()
25 #21 /var/www/public_html/lib/pkp/classes/core/PKPComponentRouter.inc.php(257): PKPRouter->_authorizeInitializeAndCallRequest
()
26 #22 /var/www/public_html/lib/pkp/classes/core/Dispatcher.inc.php(144): PKPComponentRouter->route()
27 #23 /var/www/public_html/lib/pkp/classes/core/PKPApplication.inc.php(362): Dispatcher->dispatch()
28 #24 /var/www/public_html/index.php(68): PKPApplication->execute()
29 #25 {main}
30 thrown in /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Handler/CurlFactory.php on line 200
31 [31-Oct-2023 13:34:31 UTC] PHP Fatal error: Uncaught GuzzleHttp\Exception\ConnectException: cURL error 6: Could not resolve
host: pkp.sfu.ca (see https://curl.haxx.se/libcurl/c/libcurl-errors.html) in /var/www/public_html/lib/pkp/lib/vendor/guzzle
http/guzzle/src/Handler/CurlFactory.php:200
32 Stack trace:
33 #0 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Handler/CurlFactory.php(155): GuzzleHttp\Handler\CurlFactor
y::createRejection()
34 #1 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Handler/CurlFactory.php(105): GuzzleHttp\Handler\CurlFactor
y::finishError()
35 #2 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Handler/CurlHandler.php(43): GuzzleHttp\Handler\CurlFactor
5 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/PrepareBodyMiddleware.php(37): GuzzleHttp\Handler\Proxy::Gu
zzleHttp\Handler{closure}()
215 #6 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Middleware.php(29): GuzzleHttp\PrepareBodyMiddleware->__inv
oke()
216 #7 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/RedirectMiddleware.php(70): GuzzleHttp\Middleware::GuzzleHt
tp{closure}()
217 #8 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Middleware.php(59): GuzzleHttp\RedirectMiddleware->__invoke
()
218 #9 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/HandlerStack.php(71): GuzzleHttp\Middleware::GuzzleHttp{cl
osure}()
219 #10 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Client.php(351): GuzzleHttp\HandlerStack->__invoke()
220 #11 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Client.php(162): GuzzleHttp\Client->transfer()
221 #12 /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Client.php(182): GuzzleHttp\Client->requestAsync()
222 #13 /var/www/public_html/lib/pkp/classes/xml/PKPXMLParser.inc.php(113): GuzzleHttp\Client->request()
223 #14 /var/www/public_html/lib/pkp/classes/xml/PKPXMLParser.inc.php(199): PKPXMLParser->_getStream()
224 #15 /var/www/public_html/lib/pkp/classes/db/XMLDAO.inc.php(52): PKPXMLParser->parseStruct()
225 #16 /var/www/public_html/lib/pkp/classes/site/VersionCheck.inc.php(76): XMLDAO->parseStruct()
226 #17 /var/www/public_html/lib/pkp/classes/site/VersionCheck.inc.php(44): VersionCheck::parseVersionXML()
227 #18 /var/www/public_html/lib/pkp/classes/site/VersionCheck.inc.php(175): VersionCheck::getLatestVersion()
228 #19 /var/www/public_html/lib/pkp/pages/management/ManagementHandler.inc.php(121): VersionCheck::checkIfNewVersionExists()
229 #20 /var/www/public_html/lib/pkp/pages/management/ManagementHandler.inc.php(66): ManagementHandler->context()
230 #21 /var/www/public_html/lib/pkp/classes/core/PKPRouter.inc.php(397): ManagementHandler->settings()
231 #22 /var/www/public_html/lib/pkp/classes/core/PKPPageRouter.inc.php(246): PKPRouter->_authorizeInitializeAndCallRequest()
232 #23 /var/www/public_html/lib/pkp/classes/core/Dispatcher.inc.php(144): PKPPageRouter->route()
233 #24 /var/www/public_html/lib/pkp/classes/core/PKPApplication.inc.php(362): Dispatcher->dispatch()
234 #25 /var/www/public_html/index.php(68): PKPApplication->execute()
235 #26 {main}
236 thrown in /var/www/public_html/lib/pkp/lib/vendor/guzzlehttp/guzzle/src/Handler/CurlFactory.php on line 200