SharePoint 2013, 2016 Troubleshooting - 'Sorry, we’re having trouble reaching the server'

This post explains how to troubleshoot the SharePoint 2013, 2016 error, "Sorry, we’re having trouble reaching the server"

Introduction 
 
In this blog, we will demonstrate and troubleshoot a common issue when using the People Picker web control in Sharepoint.


We are receiving an error message in the People Picker control while adding users to Sharepoint. The error message states that it could not find the users, a commonly seen problem in SharePoint 2013 and 2016.
 
Error Message: 'Sorry, we’re having trouble reaching the server.'
 
 
 
Troubleshooting:
 
- Open Central Admin, Go to Application Management
- Manage web applications
- Select Web Application, click on Authentication Providers under Security Section from toolbar
- In Authentication, Providers Click on Default
- Edit Authentication Page, Uncheck Enable anonymous access
 
 
 
In the case that the issue is still occurring, validate the below troubleshooting actions:
 
- Install “HTTP Activation roles” if not installed on your front-end servers.
Steps - Server Manager >> Add Roles and Features >> Select HTTP Activation and install.
Post-installation, Try IIS reset once from all front-end servers.
- Check Alternate Access Mappings settings for the web application.
- Validate and make sure the domain account you are using for a SharePoint service account has the necessary permissions to read domain accounts
- We can try updating "Query timeout" value from layouts folder - 15\TEMPLATE\LAYOUTS\clientpeoplepicker.js >> SPClientPeoplePicker.UserQueryMaxTimeout)
- The issue should be resolved after following the above steps. If it still occurs, try a server reboot and check the RAM/CPU status.