tried 1.0.0 and 1.0.0-grails3, actually checked the links and there is no folder for this plugin there.
| Error Error initializing classpath: Could not find org.grails.plugins:simple-captcha:1.0.0-grails3.
Searched in the following locations:
file:/home/pablo/.m2/repository/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.pom
file:/home/pablo/.m2/repository/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.jar
https://repo.grails.org/grails/core/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.pom
https://repo.grails.org/grails/core/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.jar
https://jitpack.io/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.pom
https://jitpack.io/org/grails/plugins/simple-captcha/1.0.0-grails3/simple-captcha-1.0.0-grails3.jar
| Error Error initializing classpath: Could not find org.grails.plugins:simple-captcha:1.0.0.
Searched in the following locations:
file:/home/pablo/.m2/repository/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.pom
file:/home/pablo/.m2/repository/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.jar
https://repo.grails.org/grails/core/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.pom
https://repo.grails.org/grails/core/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.jar
https://jitpack.io/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.pom
https://jitpack.io/org/grails/plugins/simple-captcha/1.0.0/simple-captcha-1.0.0.jar
tried 1.0.0 and 1.0.0-grails3, actually checked the links and there is no folder for this plugin there.