MacOS Sierra won’t install and says “An error occurred while preparing the installation. Try running this application again.”

Hi lulupeg,

We appreciate you reaching out to us.

We’d like to gather additional details that may help us be in a better position to assist you.

Have you tried macOS Recovery while using a wired internet connection?

Trying a wired internet connection can help in isolating the issue.

If the issue persists while using a a wired internet connection, another option you can try is to create a bootable installer. We'd like to set your expectations. As mentioned in the article below, "These advanced steps are primarily for system administrators and other experienced users who are familiar with entering commands in Terminal."

Create a bootable installer for macOS: Create a bootable installer for macOS - Apple Support

If you are still unable to reinstall macOS or if you are not comfortable in using the terminal, we recommend that you get the device inspected by a technician.

You can explore your service options here: Get Support

Take care!