Everything seems to be sorted. I was struggling to update Forstron to 1.9 (WordPress wouldn’t let me do so in the dashboard), so I changed the folder name of the “old” Forstron (v1.8.3) in my cPanel File Manager and uploaded v1.9 manually.
My website is now running a child theme of Forstron v1.9 and everything seems to be working.
Many thanks for your assistance. I appreciate it immensely!