Dear Joomla51 Support:
I can't get past Step #2 of the Joomla installation process. I am following the instructions from https://www.joomla51.com/tutorials/demo-installer/setting-up-the-demo-installer. I get the following error messages:

Warning
INSTL_DATABASE_HOST_IS_NOT_LOCALHOST_GENERAL_MESSAGE
Error
INSTL_DATABASE_HOST_IS_NOT_LOCALHOST_DELETE_FILE

I tried a number of different options to troubleshoot. I tried three templates from Joomla51.com, all with the same results and error message (Hayley, Emani, and Serenity). I then tried installations with the three different types of PHP versions, 7.4x was the best result. Finally, I tried MQSL and MQSLi selections during the Joomla install, same error messages. I have never had difficulty installing a template before. I very easy. Please advise as soon as possible. Thank you.