Changing war file name to old war name giving errors in tomcat

Question

We have a webapp deployed to tomcat 7.0, its name is "myapp.war". The application is accessible at localhost/myapp. Users been logging in and using it from last one year.

Now, we got an updated version as "myapp1.war". I stopped tomcat, removed war and exploded war files of the old one. Copied new war in webapps and started tomcat. The application is now accessible as localhost/myapp1 and users can work fine.

But I got asked not to change the old url, so I stopped tomcat, removed exploded war directory and renamed myapp1.war to myapp.war. After starting tomcat, the application is accessible back at old url: localhost/myapp.

However, no one is able to login and all get some JSON data error. I myself got same error, tried to use incognito mode on browser and it works fine. I deleted browser cookies and it worked fine for me in normal mode too.

I want to know why this happened and how can I fix this without asking my 100+ users to delete browser cookies. Thanks in advance.