Xcode Build Server failed. The devices configured for testing were not found

Found a solution provided by user @juce on github. Link to original response in Apple Developer Forum

Here' is a link to github post explained a details by @juke:

Copy of script:

--- deviceClass.js  2017-05-05 07:10:40.000000000 -0700+++ deviceClass.js.NEW  2017-05-05 07:13:36.000000000 -0700@@ -12,6 +12,7 @@     dbCoreClass = require('./dbCoreClass.js'),     xcsutil = require('../util/xcsutil.js'),     logger = require('../util/logger.js'),+    fs = require('fs'),     redisClass = require('./redisClass.js'); /* XCSDeviceClass object */@@ -141,12 +142,11 @@         query.endkey = [unitTestUUID, {}];     }-    redisClass.getDynamicQuery(req, doc_type, function DEVListRedisGetDynamicQuery(err, docs) {-        if (err) {-            opFailed(err);-        } else if (docs) {+    var devicesFile = '/Library/Developer/XcodeServer/Logs/xcs_devices.json';+    fs.readFile(devicesFile, 'utf8', function (err,docs) {+        if (docs) {             docs = JSON.parse(docs);-            log.info('Found', docs.length, 'devices in Redis.');+            log.info('Found', docs.length, 'devices in file-system cache.');             opSucceeded(docs);         } else {             log.debug('No devices found in Redis. Falling back to CouchDB.');@@ -167,9 +167,12 @@                 } else {                     log.info('Found', docs.length, 'devices in CouchDB.');-                    redisClass.setDynamicQuery(req, doc_type, JSON.stringify(docs), function DEVListRedisSetDynamicQuery(err, wasSaved) {-                        if (wasSaved) {-                            log.debug('Successfully cached devices to Redis.');+                    fs.writeFile(devicesFile, JSON.stringify(docs), 'utf8', function(err) {+                        if (err) {+                            log.debug('Problem saving devices into ' + devicesFile);+                        }+                        else {+                            log.debug('Successfully cached devices to file.');                         }                         // Even if there's an error (i.e. Redis suddenly went down), we can still continue since                         // the next request would be redirected to CouchDB.

How to apply. Download or copy this script, and path existing file like this:

[sudo] cd /Library/Developer/XcodeServer/CurrentXcodeSymlink/Contents/Developer/usr/share/xcs/xcsd/classes    patch deviceClass.js /path/to/xcs-tweaks/xcs-devices-patch.diff

Then restart the simulator and possibly restart your machine (that was my case). Then check if it's working by:sudo xcrun xcscontrol --list-simulators

Big thanks @juke whoever you are :)

My problem with this was that I had set up the bot on an earlier version of Xcode (with only 11.2 simulators installed).

I upgraded the version of Xcode on the machine I use to run bots, which only had 11.4 simulators installed. Changing the simulators to these latest versions fixed it.