So, um, you live in the far North; you apparently have sheer curtains in front of the window where the plant lives…
Get rid of that. Curtains block all the light, and you don't have that much to start with.
Second, moisture meters are junk; don't rely on them. Use a bamboo skewer or something like it. Every soil is going to read a little differently.
I hope the pot has adequate drainage; it's not clear from your picture.
If the roots are all near the top of of the soil column you must water it more frequently in the long days of summer (almost nothing in winter though).
In all, Hoyas are very resilient, and I would think it will recover with time and light.
