spring-boot: Project build error: Non-resolvable parent POM for spring-boot-starter-parent:pom:2.0.6.RELEASE

I’ve created a demo project in Spring Tool Suite 3.9.6.RELEASE.

In POM.xml, I’m getting the below error:

Project build error: Non-resolvable parent POM for com.example:demo:0.0.1-SNAPSHOT: Failure to transfer org.springframework.boot:spring-boot-starter-parent:pom:2.0.6.RELEASE from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.springframework.boot:spring-boot-starter-parent:pom:2.0.6.RELEASE from/to central (https://repo.maven.apache.org/maven2): connect timed out and 'parent.relativePath' points at wrong local POM

when I ran maven clean, it is generating the build errors:

The build could not read 1 project -> [Help 1]
[ERROR]   
[ERROR]   The project com.example:demo:0.0.1-SNAPSHOT (C:\ws\demo\pom.xml) has 1 error
[ERROR]     Non-resolvable parent POM for com.example:demo:0.0.1-SNAPSHOT: Could not transfer artifact org.springframework.boot:spring-boot-starter-parent:pom:2.0.6.RELEASE from/to central (https://repo.maven.apache.org/maven2): connect timed out and 'parent.relativePath' points at no local POM @ line 14, column 10 -> [Help 2]
[ERROR] 

<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
	<modelVersion>4.0.0</modelVersion>

	<groupId>com.example</groupId>
	<artifactId>demo</artifactId>
	<version>0.0.1-SNAPSHOT</version>
	<packaging>war</packaging>

	<name>demo</name>
	<description>Demo project for Spring Boot</description>

	<parent>
		<groupId>org.springframework.boot</groupId>
		<artifactId>spring-boot-starter-parent</artifactId>
		<version>2.0.6.RELEASE</version>
		<relativePath>../pom.xml</relativePath> <!-- lookup parent from repository -->
	</parent>

	<properties>
		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
		<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
		<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-tomcat</artifactId>
			<scope>provided</scope>
		</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>