OAuth2 Trouble with Redirect URL { error: 'invalid_grant', error_description: 'Redirect URI is invalid' }

Hello,

While following the steps outlined in the OAuth 2.0 authorization documentation, I am receiving the following error in Step 3 (Exchanging authorization code for access token): 

data: {
    error: 'invalid_grant',
    error_description: 'Redirect URI is invalid'
}

What I've done so far: 

1. Ensured that my request URL is free of syntactical errors: "https://login.wrike.com/oauth2/authorize/v4?client_id=${process.env.WRIKE_OAUTH2_CLIENT_ID}&response_type=code&redirect_uri=${process.env.WRIKE_OAUTH2_REDIRECT_URI}"
2. The WRIKE_OAUTH2_REDIRECT_URI value above resolves to "https://localhost:3000/auth/wrike/callback" which I have also entered in the API > API Apps configuration screen without any spelling errors
3. I originally did not have "https" on localhost, I was using "http". However, I read the paragraph under the "Redirect URI*" section on the app configuration page that says "Provide one or more redirect URIs. Redirect URI should comply with OAuth2 standard requirements and utilize HTTPS protocol. Use “https://localhost” for local development." and updated my local environment to use https accordingly

I attempted to use the permanent access token just to test a few things until I'm able to resolve the error above, and even using the permanent token is resulting in the following error:

data: {
    errorDescription: 'Authorization method unknown',
    error: 'not_authorized'
}

For the permanent token, I am using a header that looks like: "Authorization: bearer [TOKEN]"

Any help would be greatly appreciated!