Thanks for reporting this.
The "Set as active" button is automatically selected (and disabled) at the time when (cumulatively) you upload a certificate (either Development or Production) and this is the only uploaded certificate. Click "Save" at the bottom of the page when ready.
Subsequently, when you upload a new certificate you should be able to set it as active and after that click Save
to save the changes.
Additionally, yes, we fixed a few bugs inside this area last year. There are a few cases now when the platform may be disabled (and you need to enable it again with the checkbox) after managing and toggling the certificates. This said, I would like to offer the apologies of the team for any inconvenience caused and if the experience is not as expected.
Allow me to ask you a few details about the workflow you are following and when this occurs - can you please elaborate more on this with steps you are following and with the expected behavior? You can also illustrate this with screenshots. Let me know if you would like to make the thread private so you can safely share screenshots and similar.
I look forward to your reply.
Telerik by Progress