The ability to see a PR type in FinOps is decided by the Purchase Request Permissions (or Matrix).
You will need to check that your user record has been given Access to the particular PR type. This can be done in Financials.
Note: In order to follow these steps you must be logged in as a User who is in the MASTER security profile of FinOps
Click Purchasing then click Settings.
Click Purchase Request Permissions.
Select the PR type and then assign the correct permissions for the user who has lost the view of the PR type in FinOps.