Find the fatal PHP error behind this screen using the recovery email or debug logging, then fix or disable whatever is throwing it. "The site is experiencing technical difficulties" is WordPress's fatal error protection screen, replacing the old white screen of death on modern WordPress versions by catching a fatal PHP error before it takes down the whole site.
Check your email first
When this error triggers, WordPress usually emails the site administrator a direct link to a "recovery mode" that lets you log in and see which plugin or theme caused the crash without the fatal error blocking you. Check the inbox for the admin account (including spam). If you have that email, click the recovery link, log in, and WordPress will flag the exact plugin or theme responsible right in wp-admin.
If you never got the email, or can't find it, move on to reading the error directly.
Turn on debug logging to see the real error
Edit wp-config.php via FTP, or via Services → your hosting → File Manager. Find:
define('WP_DEBUG', false);
Change it to:
define('WP_DEBUG', true);
define('WP_DEBUG_LOG', true);
define('WP_DEBUG_DISPLAY', true);
Save, then reload the site. You'll either see the fatal error and its file path directly on the page, or find it logged to /wp-content/debug.log. The message names the exact file and line that failed. Set WP_DEBUG_DISPLAY back to false once you're done, so errors stop showing to visitors. This is the same debugging approach covered in more detail in Fixing the WordPress white screen of death, since both errors trace back to the same fatal PHP failure.
The three most likely causes
A plugin update or conflict
This is the most common cause by far. A plugin either shipped a bug, or two plugins conflict, or a plugin calls a PHP function that no longer exists on your current PHP version. Rename /wp-content/plugins/ to /wp-content/plugins.bak/ via FTP or File Manager, then reload the site. If it loads, restore the folder name and re-enable plugins one at a time from wp-admin, checking the site after each one, until the error returns. The last plugin you enabled is the cause: deactivate it and update or replace it.
A theme error
If disabling all plugins didn't fix it, suspect the theme. Rename your active theme's folder, for example /wp-content/themes/your-theme/ to /wp-content/themes/your-theme.bak/. WordPress falls back to the most recent default theme automatically. If the site comes back, the theme (or a recent edit to functions.php) is the problem.
A PHP version mismatch
Older plugins and themes sometimes call functions removed in newer PHP releases, and this often surfaces right after a PHP upgrade. In the portal, go to Services, click your hosting, and open the PHP Version tile. Try dropping back one version and reload the site. If that clears the error, the real fix is updating the plugin or theme to a version that supports current PHP, not staying on an old PHP version indefinitely.
If none of that works
A syntax error introduced by a manual code edit (a stray character in functions.php or a snippet you pasted in) causes the same screen. If you edited any PHP file recently, undo that edit first via FTP and recheck. Corrupted core files are rarer but possible: re-uploading fresh WordPress core files (excluding wp-content and wp-config.php) rules that out.
If you're migrating a site and this error shows up on the new install, see Migrating your WordPress site to Flashcloud for the steps that usually avoid this. And if Site Health throws warnings after you're back up, most aren't urgent, see WordPress Site Health warnings and which ones matter for which ones actually need action.
When to open a ticket
If the debug log points to a core WordPress file rather than a plugin or theme, or you've isolated the cause but don't have FTP experience to safely rename folders and edit files, open a ticket from the portal's Support section. Include the exact error text from debug.log and which plugins or theme you've already ruled out. A real person will pick it up.