Cause
The If-Match header must carry the version in quotes, for example "3".
What to do
Send the version of the last read in quotes.
application/problem+json
{
"type": "https://masnet.com/developers/errors/invalid_if_match",
"title": "Invalid If-Match",
"status": 400,
"detail": "...",
"code": "invalid_if_match",
"correlation_id": "..."
}