Clover13

OK, it's my images which were taken on an iPhone and saved as HEIC and then converted to PNG via MacOS Preview.  I did just convert the same original file with GIMP and that was able to be uploaded.  So I suspect maybe there is some type of conversion error with MacOS Preview?

I got it, thanks @Ryan Ashbrook
Whitelisted the server IP at:  Security → WAF → Tools → IP Access Rules

I figured it out now.
Successful POST
{ "\/cms\/records\/3\/": "", "key": "xxxxxxx", "category": "5", "author": "1", "fields": { "12": "Hello", "13": "Content" } } RESPONSE { "id": 11, "title": "Hello", "category": { "id": 5, "name": "Records", "url": "", "class": "IPS\\cms\\Categories3", "parentId": 0, "permissions": { "perm_id": 97, "perm_view": "*", "perm_2": "*", "perm_3": "4,3,6", "perm_4": "4,3,6", "perm_5": "4,3,6", "perm_6": "4,3,6", "perm_7": "4,3,6" } }, "fields": { "field_12": "Hello", "field_13": "Content" },  
Python code in terms of post data:
post_data = { "category": "5", "author": "1", "fields[12]": "Hello", "fields[13]": "Content", }  
I was creating a dict for fields as follows that was failing, as it wasn't in the expected format:
fields = { "12": "Hello", "13": "Content" } And then dumping it to JSON as an object and POSTing as
post_data = { "category": "5", "author": "1", "fields": fields_json, }  

Take a look at @onlyME's apps:
https://ipsappzone.com/file/6-featured-content-pro/
https://ipsappzone.com/file/17-slider-maker/

Turns out this was even easier 🤦‍♂️
Just click the X to the right of the popup at the bottom right of the screen that has the number of Quoted Posts selected.  That clears them all out.  Note you can multi Quote posts across topics and that list gets carried around.  Seems a bit odd, as you can selected quoted posts from one topic and use them in another topic where they wouldn't have any context.  Not sure if that's by design or not.

Apparently that big red X answers my question 🥴

See here:  
 

System >> Settings >> General Configuration
You'll see a toggle for Site Online.

Nevermind, was a name matching issue and mistype.  Both valid and invalid usernames appear the same in the "To" section. TIL the error message "cannot receive messages" is an indicator of an invalid username.  

OK, problem solved.  This is with a Samsung Galaxy S20 and using what appears to be a third party app (despite it saying it's using Chrome as the browser app)
I informed the member to use Chrome directly, which is included with the Samsung Galaxy S20.
Screenshot user sent me, which I'm assuming is this app:
https://play.google.com/store/apps/details?id=privacy.explorer.fast.safe.browser&hl=en_US&gl=US

It appears to be a source site issue, not something in the AdminCP.  Subsequent attempts to add it eventually work.  Sorry @Jim M, thanks for the quick reply and review!

I figured it out, thanks Randy, your links helped spark where to look.  It came down to the S3 permission sets for those objects (certain images files) were not set to public read.  Also the favicon.ico did not move over in the S3 Storage Location usage, however it was referenced by it (i.e. tried to pull from CDN/S3 but was still local on my server).  Not sure if that is a bug, but I just moved it over manually to S3 and set the public read access on the object.

FWIW, got it sorted it out forcing a manual update of the local parameter initially.  Something with CloudLinux not behaving/updating properly, host had to toggle from PHP Selector mode to MultiPHP Manager mode and things synced up properly when he went back to PHP Selector mode.

I verified this is within Tapatalk.  The "Friendship" and "Business" is merely the title of the PM, and counts as a "Content" credit in the Ranking system I'm guessing given the 10 point credit (i.e. Posted {content}) where {content} in the case of PMs is the title of the PM.
Following up with Tapatalk again as this is a problem with their PM authorization being out of sync with IPS settings/rules configured.