With acoustic guitars you will hear some strums that are really loud and some strums that aren’t quite as loud. It could be very well played but you will still have some variation between strums. Sometimes the dynamic is quite loud and a compressor sometimes just can’t get a hold of that because the difference between the loud and soft strums are just a little too great.
Use a limiter instead in this case. You can use any limiter.
An example that could work really well in acoustic guitars usually anything over 12 to 1:10-1 for sure.