Unable to view my site. I updated the app, same results

I am having trouble viewing my site. I updated the app to the newer version, but the problem persist.
What should I do? When I click View Site , this message comes up:

** Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 20480 bytes) in /app/public/wp-includes/class-wp-hook.php on line 279

The site is experiencing technical difficulties.**

Please, thank you!