Dropbox API connection not working

Experiencing the following issues when trying to add a new destination to Dropbox. Only happening on some domains and not others. All domains hosted with same company. Have tested on other hosting and works perfectly fine. Have logged support ticket with affected hosting company but they aren't providing much assistance and said to contact plugin support. Any ideas?

White Screen Issue:
1. Click on Snapshot icon
2. Click on Destinations
3. Next to Dropbox click Add New
4. Enter Destination Name "Backup To Dropbox"
5. Click Save Destination
6. You will receive a white screen where it fails to connect to Dropbox

Missing Blue Save & Cancel buttons Issue:
1. Click on Snapshot icon
2. Click on Destinations
3. Next to Dropbox click Add New
4. Enter Destination Name "Backup To Dropbox"
5. Click Save Destination (it may fail with a white screen and you may need to refresh on your browser and redo step 4)
6. Click Allow when you see the Dropbox API message "WPMU DEV Snapshot would like access to its own folder, Apps › WPMU DEV Snapshot, inside your Dropbox."
7. You will receive a white screen where it fails to connect back to WordPress
OR
7. You will see the Dropbox API connect back to WordPress but the blue Save button is missing so you can't complete the last step in the connection authorisation.