In such scenario, big chance that your cron job is stuck and you are facing issue. See your cron job using ssh and if there is any cron job is stuck then kill the pid of that purticular process and your issue will be resolved.
Log in to your account using SSH.
Run the following command to locate hanging cron jobs:
@sip4-000 ~]$ ps ufx | grep cron
The output should resemble output shown below:
root 12080 0.0 0.0 117328 460 ? Ss Mar25 5:23 crond
username 26529 0.0 0.0 103244 848 pts/0 S+ 22:33 0:00 _ grep cron
username 6876 5.0 0.3 646760 88476 ? S 15:42 20:50 /usr/bin/php /chroot/home/username/domainname.com/html/cron.php -mdefault
The first line shows the cron service running on the server.
The second line shows the command that you just ran. It matches itself when looking for the word "cron" in the running services.
Most importantly, the third line shows your Magento cron job. The cron job usually runs quickly, so if it shows up here, it is likely hanging.
You can confirm a hanging cron job by checking the second column from the right. The 15:42 20:50 shows the duration of the cron job; if this duration takes longer than an hour, then it is hanging.
To stop the cron from running, kill the command by referencing the PID. Returning to the command output, the second column from the left is the PID 6876.
Run the following command to terminate the command:
[username@sip4-000 ~]$ kill -9 6876
For More detail see the following link to kill the process.