Hello +Kaylin Dent
I'm sorry that you're experiencing problems pairing your GS5 with your Mac.
What type of wireless network are you using? Is it a home network or a corporate/university network?
As AirSync uses WiFi, you will want to ensure that your Android device has a strong and stable connection to your wireless router. The best results will be obtained if your Android device is connected to your wireless router with a "Signal strength" of "Excellent" or "Very Good" and a "Link speed" of at least 50Mbps.
If possible, use a tool like WiFi Analyzer (https://play.google.com/store/apps/details?id=com.farproc.wifi.analyzer&hl=en
) to view the wireless signals in your area. This will allow you to see sources of interference so you can set your wireless network to utilize the least used bands and channels (e.g. 5Ghz band and channels 136+140 when 2.4Ghz is crowded and channels below 100 are used by other 5Ghz devices).
Please try these AirSync troubleshooting steps.http://www.doubletwist.com/help/question/airsync-troubleshooting/
Step #3 (disable, enable AirSync) resolves the issue for many users.
Rebooting all of the devices in the network (including the wireless router) has also been successful for some users.
Also, Android 6.0 (Marshmallow) has introduced a new SD card support method. Unfortunately this new method is incompatible with apps like ClassicPlayer that used an older API to access the SD card.
We are in the process of updating the ClassicPlayer app to fully support the Android 6.0 (Marshmallow) SD card. We are also adding brand new features like material design UI, a new playback engine to include lossless support, and a more powerful EQ. The first alpha version with support for the Marshmallow SD card is now available.
IMPORTANT: This alpha does NOT include podcasts, UPnP/DLNA & AirPlay video, which will be added in the coming months. If you're using any of the missing features, do NOT upgrade to this release.
Use this link to opt into the alpha (Google login required): https://play.google.com/apps/testing/com.doubleTwist.androidPlayer