After upgrading to v8, my stacks function is not working properly. I cannot successfully add a pagelist block. I get the following error message:

Entity of type 'Concrete\Core\Entity\File\File' for IDs fID(72) was not found

What is causing this, and how can I fix this?!

I am not a developer.

Here is my environment:
# concrete5 Version
Core Version - 8.3.2
Version Installed - 8.3.2
Database Version - 20180122213656

# concrete5 Packages
Equinox (1.0.3), Fresh (0.9.6), Image Zoom ( 0.9.2), Spacer (0.9.3), Whale Grid Gallery (2.4.5), Zoomer (1.0.1)

# 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
5.6.32

# PHP Extensions
bcmath, bz2, calendar, cgi-fcgi, Core, ctype, curl, date, dba, dom, enchant, ereg, exif, fileinfo, filter, ftp, gd, gettext, hash, iconv, imagick, imap, intl, json, libxml, mbstring, mcrypt, mhash, mysql, mysqli, mysqlnd, odbc, openssl, pcre, PDO, pdo_dblib, pdo_mysql, PDO_ODBC, pdo_pgsql, pdo_sqlite, pgsql, Phar, posix, pspell, Reflection, session, SimpleXML, snmp, soap, sockets, SPL, sqlite3, standard, tidy, tokenizer, wddx, xml, xmlreader, xmlrpc, xmlwriter, xsl, Zend Guard Loader, zip, zlib

# PHP Settings
max_execution_time - 30
log_errors_max_len - 1024
max_file_uploads - 20
max_input_nesting_level - 64
max_input_time - 60
max_input_vars - 1000
memory_limit - 128M
post_max_size - 10M
sql.safe_mode - Off
upload_max_filesize - 10M
mysql.max_links - Unlimited
mysql.max_persistent - Unlimited
mysqli.max_links - Unlimited
mysqli.max_persistent - Unlimited
odbc.max_links - Unlimited
odbc.max_persistent - Unlimited
pcre.backtrack_limit - 1000000
pcre.recursion_limit - 100000
pgsql.max_links - Unlimited
pgsql.max_persistent - Unlimited
session.cache_limiter - <i>no value</i>
session.gc_maxlifetime - 7200
soap.wsdl_cache_limit - 5