Maven War file issue at tomcat server | Ubuntu

I have a problem with my WAR file. I wrote application in Java using maven with Spring boot and Spring MVC. After packaging i pushed file to an ubuntu server at path /opt/tomcat/webapps. Currently I have tho WAR files one its test sample.war and one cow.war its my main application.enter image description hereHowever, when I try to access the main page at /cow, Tomcat can't find it if I don't have an index.html file at webapps. Instead, I encounter the following error

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error 404 - Not FoundDescription The origin server did not find a current representation for the target resource or is not willing to disclose that one exists.

if i extract index.html file from /resources/templates/user/ (like in the case of the sample application) i see my login page with is at index.html but without stylesenter image description here

Where could be issue?

I expected that tomcat can find files at ** java nad resources**

I don't have web.xml because i use Spring annotations.