ha, yes, ensure you have tomcat chowned all tomcat files:
chown -R tomcat.tomcat /opt/tomcat
Also you must ensure you have the role "manager" defined, also "admin".
This is my file:
<?xml version='1.0' encoding='utf-8'?>
<tomcat-users>
<role rolename="manager"/>
<role rolename="admin"/>
<user username="normando" password="xxxxxxxx" roles="manager,admin"/>
<user username="admin" password="xxxxxxxxxx" roles="manager,admin"/>
</tomcat-users>
Restart tomcat and try again