This XML tag has an invalid value. Please fix it and resubmit.
A friend of mine noticed in his Google console that he had an error stating: This XML tag has an invalid value. Please fix it and resubmit. The error was indicating that the priority tag was the issue. The priority tag needs to have a value of between 0.0 and 1.0. For some reason, his values were 0.0 and 1, so after changing 1 to 1.0 and resubmitting the site, Google gave him the status Success.
This is a quick blog and hopefully, if anyone else comes across this error, it will help them to fix it.