Why can't I side load

My Kompakt has just arrived. I’ve updated to the latest version. Downloaded Mudita Centre to my MacBook. Plugged in my Kompakt and all looks fine. Downloaded the latest Aurora .apk file to my MacBook. Tried to transfer it via Mudita Centre. It gets to 3 or 4% then I get ‘Couldn’t Transfer File - please try again’. I’ve tried loads of times. I’ve disconnected and restarted my laptop and the phone. I’ve tried a couple of different cables. I located the WhatsApp .apk and tried that. Same problem. I tried a book. Same problem. I just can’t transfer anything to the phone even though it appears to be connected properly in Mudita Centre. Any suggestions? What am I doing wrong? Thanks

Have you preview open while loading the apk? On my Mac this sometimes blocks the loading of apks.

OMG. Thank you so much. It wasn’t Preview but that did make me look at what else I had running in the background. I think it was Dropbox. Closed that down and it worked. You’re a star. Thank you!