This usually happen if a blogspot blog was set up by an organisation & appointed a team member to handle social media activities -- which includes blog-ing using blogspot.com blogs.
If you are managing a web store on a free blog platform like this where you might have several team members assisting you to update the blog/store contents, there may be unkown account credential updates/changes applied -- it may be confusing.
To request a deceased data from Google, send this link to the deceased surviving relative & they will need to send in a request to Google to retrieve the sign-in credentials.
A relative or legal representative will need to fill this form which requires several documentations for example a copy of government issued ID & a copy of the death certificate.
In the request form, make sure Blogger (& other possible Google services) related with the blog platform is selected -- as the deceased team member might use other Google services to managed the blog's contents.
Once you have received the relevant data from the surviving relative, continue to sign in, to access the blog dashboard.
If your organisation wishes to continue to update this blog, best to assign several Authors & Admins by sending invitation from the blog's dashboard. In the future, the blog will have several references -- or sign in credentials -- to access with.
Reference: Access to Blog when Staff Member Dies