We all face these kind of issues in Eclipse and MAven. Nothing to worry. Keep trying multiple options.
1 -- Try right click on your project and choose Maven --> Update Project and then update your project
2 -- see if your project is not showing any red mark on it
3 -- keep using maven clean and package option
4 -- sometime its better to delete existing Tomcat Server from Eclipse and recreate it and add project again and publish
5 -- reboot your machine is also a better option most of the time
6 -- Maven command prompt utility is also be considered to resolve many issues
7 -- try to see if your machine has multiple web server running on same port then better manually close all of them except Tomcat
8 -- Make sure your project has Maven Dependencies attached and if not make sure you know how to add it. This error could be happened because of missing JARS. Right click your project and choose Properties --> Deployment Assemblies --> Make sure you have shown there MAVEN DEPENDENCIES folder there. (If not then add it by clicking Add --> Java Build Path Entries --> Choose Maven Dependencies
9 -- Make sure your POM file has no issue and if YES .. Try resolve them one by one. for example check first REPOSITORY section ... then DEPENDENCIES and so and so on
10 -- Sometime you need to CLEAN and BUILD your project MANUALLY ....Choose the project then click on Project menu --> CLEAN ....
11 -- Always keep your working project copy some where with complete WORKSPACE and also take backup of working MAVEN repository some where in case if you just use it back... (in some case your environment doesnot allow you to connect to certain sites and you created those JARS maually added under maven repositories, you should keep the back up , so that not to do this exercise in case of failure)
There are always other option ... Keep try and Enjoy the JAVA WORLD!
Regards
Syed Imam