How to allow 1.8 Players join your server.
There are 3 plugins needed for this to work
(ViaVersion, ViaRewind and ViaBackwards)
The steps to do this are:
(1): Access https://playerservers.com/dashboard/plugins/
(2): Locate the 'Search' bar in the top right.
(3): Search for 'Via'.
(4): Download the required plugins.
(Optional, 5): If your server is currently running use /stop and restart it
Upon joining ViaVersion, ViaRewind and ViaBackwards should be enabled and 1.8 Players should be allowed to join your server.