Today counterparty releases version 9.59.4 which includes a hotfix for a sanity error which would cause a Counterparty server to stop operating normally.
View counterparty-lib 9.59.4 Release Notes
Upgrade Procedure for those running a federated node:
cd federatednode/
fednode update counterparty counterparty-testnet
fednode rebuild counterparty counterparty-testnet
fednode rollback 698450 counterparty
fednode start counterparty