@EnableAdminServer

Oi Pedro,

Parece que o Spring Boot Admin não foi importado corretamente no projeto. Confere no pom.xml do projeto

o pom.xml está desse jeito, não vi nada de anormal.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.7.1</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>br.com.alura</groupId>
    <artifactId>spring-boot-admin</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>spring-boot-admin</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Está faltando adicionar a dependência do Spring Boot Admin Server:

<dependency>
    <groupId>de.codecentric</groupId>
    <artifactId>spring-boot-admin-starter-server</artifactId>
    <version>2.1.4</version>
</dependency>

Eu adicionei a dependência, mas apareceu este erro

Project build error: Non-resolvable parent POM for br.com.alura:spring-boot-admin:0.0.1-SNAPSHOT: Could not find artifact org.springframework.boot:spring-boot-starter-parent:pom:2.1.4 in central (https://repo.maven.apache.org/maven2) and 'parent.relativePath' points at no local POM

Posta aqui como ficou o seu pom.xml completo.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.4</version>
        <relativePath /> <!-- lookup parent from repository -->
    </parent>
    <groupId>br.com.alura</groupId>
    <artifactId>spring-boot-admin</artifactId>
    <version>0.0.1-SNAPSHOT</version> 
    <name>spring-boot-admin</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>

        <dependency>
            <groupId>de.codecentric</groupId>
            <artifactId>spring-boot-admin-starter-server</artifactId>
            <version>2.1.4</version>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

Nessa parte:

<parent>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-parent</artifactId>
    <version>2.1.4</version>
    <relativePath /> <!-- lookup parent from repository -->
</parent>

Altere a versão do Spring Boot para: 2.1.4.RELEASE

Obrigado pela atenção e ajuda.