Invalid API key

Good day ZOHO team.

Here is an issue.
There is a suspicion that Desktop Central does not add new software to Service Desk.
When I tried investigate where is the problem could be I've discovered issue with API key.
Open "ME integration" - Desktop Central and find out that API field is empty.

I have technician account and can generate API.
But after I enter generated key (tried with both - with expiration and without it) I have error message (see attachment)
"Failed to update Associated Applications details. Invalid application API Key found in input data"

Please advise what is the problem ?