Call to grep in command substitution fails - bash

Question

I am trying to make a grep call in a command substitution in bash like so:
status=$(dpkg -s elasticsearch | grep "Status")
But when I run this in a script called elk.sh, I get the following output:
./elk.sh: 47: ./elk.sh: grep: not found
It seems that when I use command substitutions, grep is not found. But when I call it normaly in my script, it is working as usual.
Do you have any idea of what could be wrong?
EDIT: as my code is not sensitive, I am sharing it here, since it may help you to understand what is wrong.
Note that file elk.sh returns:
elk.sh: POSIX shell script, UTF-8 Unicode text executable
Here is the code:
#!/bin/sh
pInfo() {
if [ "$#" -ne 1 ]; then
echo "Invalid arguments: pInfo needs one string as argument."
exit 1
fi
echo "\033[32m[INFO]\033[0m $1"
}
pError() {
if [ "$#" -ne 1 ]; then
echo "Invalid arguments: pError needs one string as arguments."
exit 1
fi
echo "\033[31m[ERROR]\033[0m $1"
}
install_elk() {
wget "https://artifacts.elastic.co/downloads/elasticsearch/elasticsearch-6.4.2.deb" -q --show-progress
sudo dpkg -i "elasticsearch-6.4.2.deb"
sudo apt-get install -f
sudo rm -rRf "elasticsearch-6.4.2.deb"
}
which grep
echo $PATH
pInfo "Verifying ElasticSearch installation."
status=$(dpkg -s elasticsearch | grep Status)
if [ "$?" -ne 0 ] || [ -z "$status" ]; then
pError "ElasticSearch is not installed."
pInfo "Start the installation ? (y/n)"
read answer
if [ "$answer" != "y" ] && [ "$answer" != "n" ]; then
pError "Invalid answer. Just type 'y' (yes) or 'n' (no)."
exit 1
fi
if [ "$answer" = "y" ]; then
pInfo "Installing ElasticSearch..."
install_elk
else
pInfo "Not installing ElasticSearch."
exit 2
fi
fi
pInfo "ElasticSearch installed."
ps ax | grep -v grep | grep "elasticsearch" > /dev/null
if [ "$?" -eq 1 ]; then
pInfo "ElasticSearch not running. Starting..."
if [ ! -z "$(ps -p 1 | grep "systemd")" ]; then
pInfo "System running systemd."
sudo systemctl start elasticsearch.service
else
pInfo "System running init."
sudo -i service elasticsearch start
fi
fi
pInfo "ElasticSearch started."
exit 0
A call to elk.sh gives the following output:
$ ./elk.sh
/bin/grep
/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
[INFO] Verifying ElasticSearch installation
[INFO] ElasticSearch installed
./elk.sh: 49: ./elk.sh: grep: not found
[INFO] ElasticSearch not running. Starting...
[INFO] System running systemd.
[INFO] ElasticSearch started.
EDIT: I found the issue: rewriting the line like so:
status=$(dpkg -s elasticsearch |grep "Status")
makes the commands works just fine. I just needed to remove the whitespace between the pipe and the grep command.