The account of site administrator was deactivated by atlassian.

[Dmitrii Olegovich]

Is there an option to reactivate this account?

If that doesn't happen. Will my account be able to become a site administrator?

[BHUSHAN PATIL]

Hi @Dmitrii Olegovich ,

Reactivating a deactivated account on Atlassian typically involves reaching out to Atlassian support team directly. They'll guide you through the reactivation process, which might involve providing additional information, resolving outstanding issues, or fulfilling certain criteria set by Atlassian.

to raise a support ticket with Atlassian: Atlassian support 
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Regarding becoming a site administrator, typically, the role of a site administrator needs to be assigned by an existing site administrator or Organization admin. The organization admin is the highest level of authorization in the cloud. He has access to the organization settings and can manage all the settings. Since the cloud functions as an instance, an organization admin is the highest admin on all products that are connected to the instance.

also refer the following KB article for more details
Enabling a deactivated account to provide site-access

Also, if you feel my input help you please accept the answer.

Regards,
Bhushan