SQL Server 2014 Replication - The process could not connect to Subscriber 'xxx'

I have just set up very basic transactional replication on SQL Server 2014.

The Publisher and Distributor are one and the same.

I have configured the Publisher to push to the Subscriber, so any and all configuration was done on the Publisher.

I set up all of the user accounts exactly as detailed in this Microsoft Tutorial.

The Publisher and Subscriber are successfully set up, and SQL Server Agent is running on both servers.

Regardless of this, when I check the status on the Publisher, I repeatedly get this message:

The process could not connect to Subscriber '(subscriber-box)'

I've checked online, including here, here, here and here.

I've tried the suggestions and can't debug it, though I am pretty sure it's logon related.