is there a way to check if invited members accepted invitation, and resend invitation if they didn't accept yet or simply deleted their invitation email?
At account level, you can try https://forge.autodesk.com/en/docs/bim360/v1/reference/http/users-GET/ to check the status of the user. New user of account should be "not_invited" status, and if this user is invited into a project, the status will be "pending" before accepting the invitation.
At project level, try https://forge.autodesk.com/en/docs/bim360/v1/reference/http/admin-v1-projects-projectId-users-GET/ to check the status of project users.
But, there seems no API available to resend the invitation.