I have set up tomcat 8 according to this, and I have the following tomcat-users.xml file:
I follwed the same tutorial but after some months I strangely got the error "403 Access Denied" while tryed to use Manager App. In this case I was using the ipaddress:8080 in the address bar and Tomcat Manager App didin't prompting for user/password. In case of localhost:8080 the error was "401", the dialogbox asking for username and password was displayed but the user not recognized.
I tried all the previous suggestions / solutions without lucky. The only way I found is been to repeat again the entire tutorial overwriting also the files. When finished, I found again the old deployed project into the webapps directory. Now Apache Tomcat/8.5.16 Manager App are working again. I do not know what happened I didn't understand also because I'm a newbie in Tomcat user