You have not give us enough information about error.
So I suggest you to check PrestaShop system requirements with this script on your host:
https://github.com/PrestaShop/php-ps-info
make sure you have all requirements and even higher than recommended values.
Then check again, If you had error again, try again with enabling debug mode and check from your browser Inspect element > Network to see what error you get in process.
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