AI Engine designs can run into simulator hangs. A common cause is insufficient input data for the requested number of graph iterations, mismatch between production and consumption of stream data, cyclic dependency with stream, cascade stream or asynchronous buffers, or wrong order of blocking protocol calls (acquisition of async buffers, read/write from streams).
By default, the x86simulation detects the deadlock (if any), and the messages that appear in the console guides you on debugging further.