What version of concrete5 are you running?

Ideally, you should post the dashboard environment report here (but that is unavailable with the site down)

Ohh yes . sure :-)

# concrete5 Version
Core Version - 8.4.5
Version Installed - 8.4.5
Database Version - 20180717000000

# concrete5 Packages
Easy Image Gallery (1.4.2), Wire (1.5)

# concrete5 Overrides
None

# concrete5 Cache Settings
Block Cache - Off
Overrides Cache - Off
Full Page Caching - Off
Full Page Cache Lifetime - Every 6 hours (default setting).

# Server Software
Apache

# Server API
cgi-fcgi

# PHP Version
7.2.34

# PHP Extensions
bcmath, calendar, cgi-fcgi, Core, ctype, curl, date, dba, dom, exif, fileinfo, filter, gd, gettext, hash, iconv, imagick, imap, intl, json, libxml, mbstring, mysqli, mysqlnd, openssl, pcre, PDO, pdo_mysql, pdo_sqlite, Phar, readline, Reflection, session, SimpleXML, soap, sodium, SPL, sqlite3, standard, sysvshm, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, Zend OPcache, zip, zlib

# PHP Settings
max_execution_time - 50
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - 60
max_input_vars - 5000
memory_limit - 8589934592
post_max_size - 256M
upload_max_filesize - 256M
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
session.cache_limiter - <i>no value</i>
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5
opcache.max_accelerated_files - 10000
opcache.max_file_size - 0
opcache.max_wasted_percentage - 5

First - use your cPanel take a backup of files and database !!

If you can use your cPanel to temporarily downgrade the php version or get your host to do that for you, do that to get the site operational. Then upgrade to 8.5.2. - I think that is the most recent auto-update. Then continue with the new php version.

If you can't get it operational by temporarily downgrading the php version, you can try a manual process (a bit dangerous if you are not familiar with it):
- copy the /concrete/ files (ie, just the core) from a new version zip (ie, 8.5.2 or 8.5.4) to your site as /new_concrete/
- rename directories so your old /concrete/ becomes /old_concrete/ and /new_concrete/ becomes /concrete/
(ie you are swapping the core /concrete/ to the new files)
This will give your site the new core code files.
- visit the site and it should run - because it has the new files. In the background it should automatically make any necessary database updates.

Once you are sure it is working, delete /old_concrete/.

Ill venture your host is Hostmonster.
Looks like they changed the version without telling anyone.