There are some common reasons to getting this error. You can follow this solutions.
- If you are using any local server / localhost then you will get this due to memory limit. So, please increase your memory limit then try again.
- If not, please try to deactivate the ‘One Click Demo Import Plugin’ and reactivate it. After that try to import the demo again.
- If not then try to use a fresh WordPress install and try to Import the demos again.
- If not, Try to change the PHP versions
- If not, then please contact your hosting provider.
Note: You can try on a staging server. Like https://tastewp.com/
If you get working LocalPress on https://tastewp.com/ then please change your hosting provider.