Please note that changes in how the Dropbox API works will result in temporary issues with the Dropbox Login and Sync. If you are already logged into Dropbox, you may start to see alerts about a “Dropbox Error”. And if you are trying a fresh login to Dropbox from the ServicePlanner settings it will just time out.
I say that this is a temporary issue because an update to ServicePlanner is in the final stages of testing that resolves this issue. I hope to have it available on the App Store within the next few days.
In the meantime, you can go into Settings > Dropbox Sync, and disable the “Auto Sync” if you want to stop any alerts. And please use the Manual Backup option available in Settings if you are worried about losing any data or want to manually sync to another device.