I suspect this is a php version incompatibility. I think c5's core (and probably some add-ons) used to use Object, but then Object became reserved in php so the core and add-ons had to be changed. Perhaps something in your installation (core_commerce?) has not been updated to keep up with such changes.

Your current version of Core Commerce is not PHP7 compliant.
You should upgrade your package to version 2.8.18 (attached)

Thanks! I'm traveling this week so it may be while before I get to this.

I'll let you know how things go.

No problem, I have tested the attached package for PHP7 compliance and found no errors.

Unzipped files as directed but did not see in 'add functionality'. Any way to force installation? Still getting this message...

Warning: Declaration of CoreCommerceProductAttributeKey::load($akID) should be compatible with Concrete5_Model_AttributeKey::load($akIdentifier, $loadBy = 'akID') in /home/maccap2/public_html/packages/core_commerce/models/attribute/categories/core_commerce_product.php on line 15

Fatal error: Class 'Object' not found in /home/maccap2/public_html/packages/core_commerce/models/product/model.php on line 5

Success (I think.)

I replaced the files throwing errors and/or warnings.

So far, so good.

Thanks to everyone who replied.

There are details on the changes needed to make eCommerce for c5.6 run on php7.2 on my site athttps://www.c5magic.co.uk/add-ons/zone-based-shipping/php7/...