In the last couple of months we have purchased quite a few themes from Themeforest, and all of the themes had huge amount of problems when installing and importing demo data. One of the themes had a request of increasing the max execution time to 40000, and our host provider only supports up to 7800. The amount of time spent - first of all buying the theme trusting that it will not give problems - and then getting errors upon errors when installing and importing demo data and then having to phone your host provider to try and help but with no luck. Time is money and we cannot wait 2 days for support to get back with some form of help! Is it still worth buying themes on Themeforest?
Depending on your hosting provider, you may have some limitations if it’s hosted in the same country as yours. Maybe it’s the hosting???