It seems, you need to add few of the domains in the whitelisted settings.
As per this Allow the Required Domains :
If you control your users’ or servers’ access to the Internet through
allowlists, add these domains to ensure that you receive all
you need to upload a single file that contains the SSL cert, Intermediate CA, and then the Root CA in that order.
You can place your URL in Check SSL
1: https://www.sslshopper.com/ssl-checker.html And can notice all the certificate errors.
For further reference check this article too Merge a complete certificate chain for custom HTTPS domains
Without looking into their Oauth 2.0 implementation it is hard to tell if this is a problem in the API implementation.
Also, it is important to understand what is the duration of refresh token. If the refresh token expiration is set to 7 days only then it is not good to use of refresh token. The refresh token should have an expiration of 1 year at least. For ...
You may want to look at Web to Any. It's supposed to be simple, free, and does exactly what it says on the tin (note: I haven't tested this personally, you'll want to do your own research). Other AppExchange products also exist in various capabilities and costs. If you still insist on doing it yourself, you'll want to look at the REST API documentation. You ...
For 2, you can schedule refreshes of your extract using Tableau Online or Server: https://help.tableau.com/current/online/en-us/schedule_add.htm
You can set it up to be hourly/daily etc.
And for the last question, once you created the Tableau viz, you can use the Document API to update the connection. You will also need the REST API to download the workbook. ...
Definition Account-Level / user-Level Connection
In your current setup, you have completed Account-Level Connection via the API User / System User pair, so you see most things working just fine.
You have not established User-Level Connection for the API user / System User pair. If you have no problem, I would say there is no need to do anything.