Hi Bharat,
I tried to follow your steps. Here are the issues I am encountering. As a consequence, I am hard stuck.
I tried two ways.
- With a Global Administrator for the tenant of the subscription
- With the Account Adming of the subscription.
Unfortunately none of them worked.
For Road 1) Signed in as Global Admin
I get

<PII Removed>
this user is actually not an owner of the subscription. As Global Admin, I cannot add myself to the subscription because the options are greyed out:

So I tried Road 2) Signing in as a Account Admin, who also happens to be a Global Admin on this tenant.

<PII Removed>
Here I can at least navigate to the menu of adding other admins but it ends with an error message because the subscription is disabled:

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When I try to follow the steps of removing the spending limit (by clicking on Re-Active Subscription). I end up eventually with the following message:

Telling me to contact the Account Administrator, which you can see from above screenshot is me.
I do not know what to do next. Please advise.
Best regards,
Robert