Solved ProtocolLib? ProtocolLib-API?

This means you don't use ProtocolLib-API.

There was a ProtocolLib-API module before version 4.5.0
Now you only use

repo:

Code (Text):

<repositories>
  <repository>
    <id>dmulloy2-repo</id>
    <url>https://repo.dmulloy2.net/nexus/repository/public/</url>
  </repository>
  <!-- And so on -->
</repositories>

depend:

Code (Text):

<dependencies>
  <dependency>
    <groupId>com.comphenix.protocol</groupId>
    <artifactId>ProtocolLib</artifactId>
    <version>4.5.0</version>
  </dependency>
  <!-- And so on -->
</dependencies>

Edit you dont need the maven modules. You can always just add ProtocolLib to your build path

 

It sounds like the author is no longer supporting the API past 4.5.0.

 

No that is just from 4.5.0 the separate API isn't provided anymore. Compare it with Bukkit (API) and CraftBukkit (Implementation). The developers decide not to have a separate API. Just dropping support for Bukkit as a development dependency. After the drop you need to depend on the implementation.