Bash Backup script: Permission denied

I have written a backup script for my linux machine that encrypts the tarball and sends it to a remote server with scp with configured ssh key pairs, but it gives me the following error when i run it: ./backup_script.sh: line 27: /home/zero/Backup/backup_20230731_1251.tar.gz.gpg: Permission denied

#!/bin/bash

# Define the date format for the filename
datetime=$(date +"%Y%m%d_%H%M")

# Define the source directory and the backup directory
src_dir="/var/www/html" # this is the directory that we will back up
backup_dir="/home/zero/Backup" # This is where we will temporarily store the encrypted backup data

# Create a tarball of the source directory
tar -czf $backup_dir/backup_$datetime.tar.gz $src_dir

# Read the password from a secure file
password=$(cat /home/zero/Backup/pwd)

# Encrypt the tarball using openssl
gpg --pinentry-mode=loopback --passphrase $password --symmetric --cipher-algo AES256 --output $backup_dir/backup_$datetime.tar.gz.gpg $backup_dir/backup_$datetime.tar.gz

rm $backup_dir/backup_$datetime.tar.gz

# Get the .gpg filename 
filename=$(find /home/zero/Backup -type f -name "*.gpg" -print -quit)

# Check if a file was found
if [ -n "$filename" ]; then
	# if file is found send it ove ssh to the remote server
	send=scp $filename root@178.79.148.186:/root/Backup
        echo "$(date): Backup Successful" >> /home/zero/Backup/backup.log
	# remove file once it has been sent to remote server
	rm -f $filename
else
	# if file is not found display error msg 
    echo "$(date): No encrypted file found" >> /home/zero/Backup/backup.log
fi

The backup is made successfully, and the encryption works perfectly but it wont send to the remote server. I made the script in the root profile and i am running it as root. Here are the file permissions:

drwxr-xr-x  2 zero zero  4096 Jul 31 12:51 .
drwx------ 37 zero zero  4096 Jul 31 12:40 ..
-rw-r--r--  1 root root  3578 Jul 31 12:50 backup_20230731_1250.tar.gz.gpg
-rw-r--r--  1 root root  3578 Jul 31 12:51 backup_20230731_1251.tar.gz.gpg
-rw-r--r--  1 zero zero    96 Jul 31 12:51 backup.log
-rwx------  1 root root  1465 Jul 31 12:51 backup_script.sh
-rw-------  1 root root     5 Jul 29 04:13 pwd

My question is: How do i make it send to the remote server?

I have tried changing file permissions but i have had no luck.

This is the fix i have come up with in the end. Thanks to this answer https://stackoverflow.com/a/76803519/20177543 mentioning that it doesn't have execute permissions

# Check if a file was found
if [ -n "$filename" ]; then
	# if file is found send it over ssh to the remote server
	chmod +x $filename
	scp $filename root@178.79.xxx.xxx:/root/Backup
	if [ $? -eq 0 ]; then
		echo "$(date): Backup Successful" >> /home/zero/Backup/backup.log
		# remove file once it has been sent to remote server
		rm -f $filename
	else
		echo "$(date): Error occurred while sending backup to remote server" >> /home/zero/Backup/backup.log
	fi
else
	# if file is not found display error msg 
    echo "$(date): No encrypted file found" >> /home/zero/Backup/backup.log
fi

    send=scp $filename root@178.79.148.186:/root/Backup

You forgot the command substitution syntax here, and it's trying to execute $filename as a command.
I presume at this point that filename= /home/zero/Backup/backup_20230731_1251.tar.gz.gpg and it doesn't have execute permissions.