Most likely cause of this issue is that the PHP’s memory_limit is set lower than what is required to make Elementor plugin run efficiently.
In order to fix it, the memory_limit value for PHP would need to be increased it to typically 512M. To do the same, please checkout our this FAQ : How to override or specify PHP INI directives
Then while setting the directive(s), add the following line
When you submit the directives, the FPM for the corresponding VHost/Website would be restarted and the valid new values would take effect.