Upgrade From V3.0.6 To V4.1.5 Blank Page Problem!

[color=#555555]Hi, i installed v4 in a sub folder of the same parent folder of v3, and them use store importer to move data to v4, but when importing, it stopped at converting orders… I then tried some methods from knowledge base and revise php.ini in server, refresh the importing page and it shows finished.[/color]

[color=#555555]After that I tried to move all datas from V4 folder to overwrite the V3 folder, and revise config.local.php in V3 root to meet http/https path etc… Following cs-cart KB tips. Store admin also changed–Stores–URL to [/color]www.xx.com[color=#555555].[/color]

[color=#555555]However, I cleared cache and open [/color]www.xx.com[color=#555555], it always shows store closed, and I can't access[/color]www.xx.com/admin.php[color=#555555] too. It shows the same closed page.[/color]

[color=#555555]What is the problem? Please help asap, we're a live store and paid you 2 times so expensive liscense fee $385! When we use V3.0.6, it shows error and down several times, if V4 can't solve problem, we will give up cs-cart.[/color]

[color=#555555]Used prestashop and opencart,never meet so big problem! Our server is VPS of hostgator.We have only 1300 products but CS-cart database is about 120MB large.[/color]