Python virtual environment not activating from bash script - python-3.x

Question

Now before you mark this as a duplicate, I have tried the solution posted here and they aren't working for me. I tried making an alias and I tried creating a function as so:
activate () {
echo Activating Virtual Environment...
source alexa/bin/activate
}
activate
But my script just gets run through without a virtual environment getting activated. The script is being run from the same directory as my virtual environment directory, alexa.
For clarity, the other solution I tried was to make an alias:
alias activate="source alexa/bin/activate"
activate
That didn't work and gave me an error that ./alexaEnvSetup.sh: line 43: activate: command not found.
Any thoughts or ideas?
EDIT: I think it is worth mentioning that the echo command does print out when I do this. So the function is getting entered. The virtual environment is just not getting activated.
EDIT: Adding full code:
#!/bin/bash
if [[ "$OSTYPE" == "linux-gnu" ]]; then
echo Operating system: Linux
elif [[ "$OSTYPE" == "darwin"* ]]; then
echo Operating system: Mac OSX
echo
# Install Python 3.6.5 using `curl`
curl -O https://www.python.org/ftp/python/3.6.5/Python-3.6.5.tgz
tar xf Python-3.6.5.tgz
cd Python-3.6.5
./configure
make
make install
echo
echo Python Version 3.6.5 Installed
echo
# Install Pip
curl -O http://bootstrap.pypa.io/get-pip.py
/usr/local/bin/python3.6 get-pip.py
echo
echo Pip Installed
echo
# Install virtualenv
pip install virtualenv
echo
echo Virtual Environment Installed
virtualenv -p python3 alexa
echo Created Virtual Environment, \"alexa\"
activate () {
echo Activating Virtual Environment...
source /Users/XXXX/Auto-Lab/Commerce/alexa/bin/activate
}
export -f activate
activate
echo Virtual Environment, \"alexa\", Created and Activated
echo
# All packages (time, urllib, and json) should come default with Python3
elif [[ "$OSTYPE" == "cygwin" ]]; then
# POSIX compatibility layer and Linux environment emulation for Windows
echo Operating system: Cygwin
elif [[ "$OSTYPE" == "msys" ]]; then
# Lightweight shell and GNU utilities compiled for Windows (part of MinGW)
echo Operating system: Msys
elif [[ "$OSTYPE" == "win32" ]]; then
echo Operating system: Windows32
elif [[ "$OSTYPE" == "freebsd"* ]]; then
echo Operating system: FreeBSD
else
echo Operating system unknown.
fi

Answer 1

use the full path to the activate script in the function: source /path/to/activate
export the function: export -f activate
ensure the script is a bash script: #!/bin/bash

Answer 2

The following works for me using Anaconda virtual env, perhaps it will work with yours also?
#!/usr/bin/env bash
# do bash stuff
# Python env
PATH=/home/username/path/to/activate/bin
python -u /script/to/run