Reactivate the account:

Financials > General Ledger Menu > Set Up/Chart of Accounts > Account Master

Alternatively, users can be given access to post to Inactive accounts:

System Administration > Security > User Attributes

Search for the User
Under the Roles tab, click to highlight the role to be updated
Click Edit Role at the bottom of screen
Double-click the General Ledger yellow folder
Click Update
Enable Allow posting to inactive accounts, if desired (optional)
Enable Allow access to inactive accounts from under the Data Access section, if desired. Set to Full or Limited. If Limited, access to account segment ranges must be defined from within the corresponding folder.
Click Accept.

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