GRAFT Community Mining Pool (http://grftpool.com) has been updated to comply with the upcoming major network update which will change the hashing algorithm on April 14 (block 65110). In order to continue mining (even now, before the network update took place) you should update your miner’s configuration (and software if necessary) to be compliant with the recent changes. The new version of the miner with the new configuration is supposed to continue working after the network update as well, without additional changes.
You should change the current mining algorithm setting from “graft” (if you use XMR-Stak miner) or “cryptonight” (for other miners) to “monero7”. If your version of miner doesn’t support this algorithm, you need to update it to the latest version. Almost all popular miners already support “monero7” algorithm.