Debugger configuration for Symfony on a Laravel/Homestead virtual

I'm getting an error trying to validate my debug set up.  Here's what I'm using:

1. PHPStorm 1.2018.4 on Mac OS High Sierra.
2. A Laravel/Homestead virtual run via Vagrant.
3. Symfony 4.0 project, root locally at /User/MYACCOUNT/projects/Symfony4/symfony-01.
4. Local directory is mounted on the virtual as /home/homestead/symfony-01.
5. Using php 7.2, fpm, via nginx with root of /home/vagrant/symfony-01/public
6. php.ini for 7.2 is set up
7. Vagrant box is networked as 192.168.10.10, with my host Mac as 192.168.10.1.
8. php.ini is set up as per the instructions on the PHPStorm confluence wiki, xdebug.remote_host=192.168.10.1

Symfony comes up on my mac at 192.168.10.10, so the default Homestead set up looks valid.  But when I try the validate button, I get this (pretty uninformative) error:

"Specified URL is not reachable, caused by symfony-01.local (...)  [note: this is defined in /etc/hosts and maps to 192.168.10.10]

>>>
Validation script was created but it cannot be executed, check possible reasons:
  * Configured 'Url to validation script' is incorrect
  * Validated Web Server is not running.
  * Target directory for validation script is not public.

<<<

Settings on the dialog:

"Remote webserver"

"Path to create validation script:  /Users/MYACCOUNT/projects/Symfony4/symfony-01/public/"

Settings for the deployment host:

Connection:

• "Local or mounted folder"
• "Upload/download:  /Users/MYACCOUNT/projects/Symfony4/symfony-01"
• "Webserver root URL: http://symfony-01.local"

Mapping:

• Local path: /Users/MYACCOUNT/projects/Symfony4/symfony-01
• Deployment path on server: public
• Web path on server: /
• Project URL:  http://symfony-01.local/

I'm puzzled by the errors, which are not helping me see what exactly is the problem with these settings.  How do I proceed?