[Resolved] Missing dependencies! Run the following command to fix

I installed LibreNMS as an OVA and it has worked for close to a month with out issue. When going to the web page it gives the error

Error: Missing dependencies! Run the following command to fix:

./scripts/composer_wrapper.php install --no-dev

I ran the command suggested and get the following output which did not correct the issue:

LibreNMS\ComposerHelper::preInstall
Loading composer repositories with package information
Installing dependencies from lock file
Your requirements could not be resolved to an installable set of packages.

Problem 1
- Installation request for erusev/parsedown 1.7.1 -> satisfiable by erusev/parsedown[1.7.1].
- erusev/parsedown 1.7.1 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
Problem 2
- Installation request for laravel/framework v5.4.36 -> satisfiable by laravel/framework[v5.4.36].
- laravel/framework v5.4.36 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
Problem 3
- laravel/framework v5.4.36 requires ext-mbstring * -> the requested PHP extension mbstring is missing from your system.
- oriceon/toastr-5-laravel dev-master requires illuminate/session >=5.0.0 -> satisfiable by laravel/framework[v5.4.36].
- Installation request for oriceon/toastr-5-laravel dev-master -> satisfiable by oriceon/toastr-5-laravel[dev-master].

To enable extensions, verify that they are enabled in your .ini files:
- /etc/php.ini
- /etc/php.d/bz2.ini
- /etc/php.d/calendar.ini
- /etc/php.d/ctype.ini
- /etc/php.d/curl.ini
- /etc/php.d/dom.ini
- /etc/php.d/exif.ini
- /etc/php.d/fileinfo.ini
- /etc/php.d/ftp.ini
- /etc/php.d/gd.ini
- /etc/php.d/gettext.ini
- /etc/php.d/gmp.ini
- /etc/php.d/iconv.ini
- /etc/php.d/json.ini
- /etc/php.d/mcrypt.ini
- /etc/php.d/mysqli.ini
- /etc/php.d/pdo.ini
- /etc/php.d/pdo_mysql.ini
- /etc/php.d/pdo_sqlite.ini
- /etc/php.d/phar.ini
- /etc/php.d/posix.ini
- /etc/php.d/shmop.ini
- /etc/php.d/simplexml.ini
- /etc/php.d/snmp.ini
- /etc/php.d/sockets.ini
- /etc/php.d/sqlite3.ini
- /etc/php.d/sysvmsg.ini
- /etc/php.d/sysvsem.ini
- /etc/php.d/sysvshm.ini
- /etc/php.d/tokenizer.ini
- /etc/php.d/xml.ini
- /etc/php.d/xml_wddx.ini
- /etc/php.d/xmlreader.ini
- /etc/php.d/xmlwriter.ini
- /etc/php.d/xsl.ini
- /etc/php.d/zip.ini
You can also run php --ini inside terminal to see which files are used by PHP in CLI mode.

I have run validate.php and corrected a few errors it had. Schema error and other things

====================================

Component Version
LibreNMS 1.39-34-g303336b
DB Schema 249
PHP 7.0.9
MySQL 5.5.47-MariaDB
RRDTool 1.4.8
SNMP NET-SNMP 5.7.2

====================================

[OK] Composer Version: 1.6.5
[OK] Dependencies up-to-date.
[OK] Database connection successful
[FAIL] Database: incorrect column (notifications/datetime)
[FAIL] Database: incorrect column (users/created_at)
[FAIL] We have detected that your database schema may be wrong, please report the following to us on IRC or the community site (https://t.libren.ms/5gscd):
[FIX] Run the following SQL statements to fix.
SQL Statements:
ALTER TABLE notifications CHANGE datetime datetime timestamp NOT NULL DEFAULT ‘1970-01-02 00:00:00’ ;
ALTER TABLE users CHANGE created_at created_at timestamp NOT NULL DEFAULT ‘1970-01-02 00:00:01’ ;
[FAIL] Missing PHP extension: mbstring
[FIX] Please install mbstring

The last error is what I am having issues correcting: “Missing PHP extension: mbstring”

However, I cannot find any instruction on correcting this specific error.

Any help or direction would be helpful. I hope I do not have to start from the beginning.

Thank you

Depends on your distro

apt-get install php-mbstring
yum install php70w-mbstring

This means you need to run apt/yum install php-mbstring (where php-mbstring is the correct package name for the version of php you have installed).

On Ubuntu you need to phpenmod mbstring too I think.

Thank you. It is all resolved. Laf and Murrant, your suggestion put me on the correct path.