Always get "Active: failed" on 'sudo systemctl status mongod' command - mongodb

Question

I followed this link to install MongoDB on my machine. Everything was fine and it worked.
Currently, when I run sudo systemctl status mongod, I get this error:
● mongod.service - High-performance, schema-free document-oriented database
Loaded: loaded (/lib/systemd/system/mongod.service; enabled; vendor preset: enabled)
Active: failed (Result: exit-code) since سه<U+200C>شنبه 2019-05-21 15:50:14 +0430; 25min ago
Docs: https://docs.mongodb.org/manual
Process: 5278 ExecStart=/usr/bin/mongod --config /etc/mongod.conf (code=exited, status=1/FAILURE)
Main PID: 5278 (code=exited, status=1/FAILURE)
مه 21 15:50:14 [my-username] systemd[1]: Started High-performance, schema-free document-oriented database.
مه 21 15:50:14 [my-username] systemd[1]: mongod.service: Main process exited, code=exited, status=1/FAILURE
مه 21 15:50:14 [my-username] systemd[1]: mongod.service: Unit entered failed state.
مه 21 15:50:14 [my-username] systemd[1]: mongod.service: Failed with result 'exit-code'.
This is what I have done after it was ok, that might have caused the problem:
I decided to add mongodb extension using pecl.
I was not able to make a new database, neither by MongodDB Compassm, nor by Sell.
I uninstalled it.
I installed it from the same link and ran the same commands, but when I wanted to install it again, after running sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv 0C49F3730359A14518585931BC711F9BA15703C6
command, I got gpg: unchanged: 1 at the end, not gpg: imported: 1 (RSA: 1) which I got for the first time.
I even deleted and recreated my dbPath folder (/var/lib/mongodb) which seems that the problem is somehow associated with this parameter which is on /etc/mongod.conf.
When I run sudo systemctl status mongod, I still get Active: failed.
What should I do to run MongoDB properly again and make its status Active: Running?
Update: This is my /etc/mongod.conf file:
# mongod.conf
# for documentation of all options, see:
# http://docs.mongodb.org/manual/reference/configuration-options/
# Where and how to store data.
storage:
dbPath: /var/lib/mongodb
journal:
enabled: true
# engine:
# mmapv1:
# wiredTiger:
# where to write logging data.
systemLog:
destination: file
logAppend: true
path: /var/log/mongodb/mongod.log
# network interfaces
net:
port: 27017
bindIp: 127.0.0.1
#processManagement:
security:
authorization: "enabled"
#operationProfiling:
#replication:
#sharding:
## Enterprise-Only Options:
#auditLog:
#snmp:

Answer 1

I solved the problem by uninstalling MongoDB and installing a specific version of MongoDB, not the latest version, using this link. This might not be the actual solution but works for now.