Your screenshot shows "waiting for next available executor" so try increasing the number of executors in jenkins ("Manage Jenkins" -> "Configure System" -> "# of executors").

Also here the info how to create Swapfile (for avoiding out of memory on building large docker containers etc.). The example creates 4G swapfile at location /myswap :

sudo dd if=/dev/zero of=/myswap count=4096 bs=1MiB
sudo chmod 600 /myswap
sudo mkswap /myswap
sudo swapon /myswap

to check swap is working:

swapon -s

enable swap at boot, add line to fstab file:

sudo nano /etc/fstab

Add this line:

/myswap   swap    swap    sw  0   0

Lack of swap does not prevent building. If you are using kubernetes (given the tag in your question) you need to look at the Jenkins log, it will say why a container could not be created

Kubernetes strongly recommends to disable swap on nodes, so it's ok that free swap space is shown as 0B.