bash does not recognize if conditions within a for loop for each element for an array of strings

Goal

I am using whiptail to let the user insert passwords to files which are used in conjunction with envsubst for some template files.

whiptail checklist

in order to render stuff in whiptail I use the following:

declare -A availableServices=(
    [grafana]="Grafana Dashboard"
    [influxdb]="InfluxDB v1.x TSDB"
    [node-red]="Node-RED Flow UI"
    [portainer]="Portainer Container Mgmt"
)

# Render TUI
function askGenerateCredential() {
    local message="Set Password for particular Servicen
                Press <SPACEBAR> to Select n
                Press <Enter> to Skip
                "
    local arglist=()
    
    # Generate a String for Whiptail Checkboxes
     # FORMAT: "<INDEX> <DESCRIPTION> <OFF>"
    for index in "${!availableServices[@]}";
    do
        # Default all Services are NOT-Selected (OFF)
        arglist+=("$index" "${availableServices[$index]}" "OFF")
    done
    SELECTED_SERVICES+=$($WHIPTAIL --title "Available Services within Populo" 
                --notags --separate-output 
                --ok-button Next 
                --nocancel 
                --checklist "$message" $LINES $COLUMNS $(( LINES - 12 )) 
                -- "${arglist[@]}" 
                3>&1 1>&2 2>&3)
}

the SELECTED_SERVICES is an array declared as

declare -a SELECTED_SERVICES=()

The rendering works well, however I have a specific if else condition in my script that is unable to execute specific commands based on the selected service in the array above.

askGenerateCredential
if [ -z "$SELECTED_SERVICES" ]; then
    echo "No Services were selected. Exiting..."
    exit 1
else
    for service in "${SELECTED_SERVICES}";
    do
        if [ "$service" == "influxdb" ]; then
            echo "Setting Credentials for InfluxDB"
            setInfluxDBCredentials
        elif [ "$service" == "grafana" ]; then
            echo "Setting Credentials for Grafana"
            setGrafanaCredentials
        elif [ "$service" == "node-red" ]; then
            echo "Setting Credentials for node-RED"
            setNodeRedCredentials
        elif [ "$service" == "portainer" ]; then
            echo "Setting Credential for Portainer"
            setPortainerCredentials
        fi
    done
fi

Upon adding the above block, my script exits with 0 code when I select multiple values via whiptail UI. On the contrary, when I only select one value in the UI, the respective function is called.

What am I doing wrong here? I wish that depending on the service variable, the respective function is called and not exit the script.

Code

#!/bin/env bash

WHIPTAIL=$(which whiptail)

if [ -z $WHIPTAIL ]
then
    echo "This script requires whiptail to render the TUI."
    exit 1
fi

declare -a SELECTED_SERVICES=()

LINES=$(tput lines)
COLUMNS=$(tput cols)


declare -A availableServices=(
    [grafana]="Grafana Dashboard"
    [influxdb]="InfluxDB v1.x TSDB"
    [node-red]="Node-RED Flow UI"
    [portainer]="Portainer Container Mgmt"
)

function askGenerateCredential() {
    local message="Set Password for particular Servicen
                Press <SPACEBAR> to Select n
                Press <Enter> to Skip
                "
    local arglist=()
    
    # Generate a String for Whiptail Checkboxes
     # FORMAT: "<INDEX> <DESCRIPTION> <OFF>"
    for index in "${!availableServices[@]}";
    do
        # Default all Services are NOT-Selected (OFF)
        arglist+=("$index" "${availableServices[$index]}" "OFF")
    done
    SELECTED_SERVICES+=$($WHIPTAIL --title "Available Services within Populo" 
                --notags --separate-output 
                --ok-button Next 
                --nocancel 
                --checklist "$message" $LINES $COLUMNS $(( LINES - 12 )) 
                -- "${arglist[@]}" 
                3>&1 1>&2 2>&3)
}

function setInfluxDBCredential() {
    echo "set admin password env var for influxdb"
}

function setGrafanaCredential() {
    echo "set admin password env var for grafana"
}

function setNodeRedCredential() {
    echo "set admin password env var for node-REd"
}

function setPortainerCredential() {
    echo "set password file for portainer"
}

askGenerateCredential
if [ -z "$SELECTED_SERVICES" ]; then
    echo "No Services were selected. Exiting..."
    exit 1
else
    for service in "${SELECTED_SERVICES}";
    do
        if [ "$service" == "influxdb" ]; then
            echo "Setting Credentials for InfluxDB"
            setInfluxDBCredentials
        elif [ "$service" == "grafana" ]; then
            echo "Setting Credentials for Grafana"
            setGrafanaCredentials
        elif [ "$service" == "node-red" ]; then
            echo "Setting Credentials for node-RED"
            setNodeRedCredentials
        elif [ "$service" == "portainer" ]; then
            echo "Setting Credential for Portainer"
            setPortainerCredentials
        fi
    done
fi

EDIT

Upon suggestion I tried ${SELECTED_SERVICES[@]} in the for loop and added an echo "$service" which is able to loop through the array however the if conditions are not triggered.