I have a model of a dock which includes the dock, building, bench, bike rack etc and also a row of tires along the edge of the dock made from a single tire and then applying an array modifier so that there are multiple tires along the edge of the dock. When I attempt to reduce the collection to a single node (select All, Ctrl J) the array disappear and I am left with a single tire. What do I need to do to overcome this?
and then choose apply. If you then tap CTRL J to join it should work.
You can provide your blend file by opening https://blend-exchange.com/ and then follow instructions.