Hey Strodo and Feline, I had this issue as did someone else here who had reached out for assistance and I found this to be most helpful, assuming you are both using Unity 2020 :)
https://forum.unity.com/threads/changes-to-the-webgl-loader-and-templates-introduced-in-unity-2020-1.817698/
Switching on Decompression Fallback worked for me :)
PB
