Thank you for your reply.
I try flash newest firmware update, dont help.
When i try unpluged one hashboard mining dont start, i dont know how to test hashboard one by one.
2025-12-27 13:34:10 [INFO_] commit version: 6eae4985e2fdb7f57d8220024fe3763f6a54647f 2025-04-22 15:03:49, build by: jenkins 2025-04-22 15:23:42
2025-12-27 13:34:10 [INFO_] platform[AML]
2025-12-27 13:34:10 [INFO_] miner type[Antminer S21+] firmware type[Release] compile time[Tue Apr 22 15:05:57 CST 2025]
2025-12-27 13:34:10 [INFO_] firmware version[FR-1.15(250422-S21+)]
2025-12-27 13:34:10 [INFO_] SN[HQDZG4UBEJBJE019N]
2025-12-27 13:34:10 [INFO_] MAC[02:87:95:A3:65:C5]
2025-12-27 13:34:10 [INFO_] work mode[NEM_MODE]
2025-12-27 13:34:18 [INFO_] power version[0x00c1] sn[DGAH347BEJBAB0714] calibrated[true] c_date[211208]
2025-12-27 13:34:18 [INFO_] only 2 boards plug in
2025-12-27 13:34:18 [ERROR] board num is not enough
2025-12-27 13:34:18 [ERROR] err code[J:8]
2025-12-27 13:34:18 [ERROR] S21+ setup err
2025-12-27 13:34:18 [ERROR] ---[S21PT1_BOARD_NUM_ERR]
This is first log after issue
2025-12-26 17:13:25 [INFO_] 30m miner hashrate[206157.21] board[0] hashrate[73881.68] board[1] hashrate[67342.03] board[2] hashrate[64933.49]
2025-12-26 17:37:20 [WARN_] power watt change too fast, last[4879] now[0]
2025-12-26 17:37:32 [ERROR] feedback voltage[0.00] allowed band max[12.99] min[10.63] status[2097152]
2025-12-26 17:37:32 [INFO_] miner restart
2025-12-26 17:37:32 [INFO_] kill all hashboard
2025-12-26 17:37:33 [INFO_] start to check network
2025-12-26 17:37:37 [INFO_] cooling the boards, please wait, this may take up to 5 minutes...
2025-12-26 17:41:33 [INFO_] bring up temperature[26.00] diff[3.00]
2025-12-26 17:41:41 [INFO_] board[0]: asic num[55] times[0]
2025-12-26 17:41:42 [INFO_] board[1]: asic num[55] times[0]
2025-12-26 17:41:42 [INFO_] board[2]: asic num[55] times[0]
2025-12-26 17:46:22 [INFO_] kill all hashboard
2025-12-26 17:46:23 [ERROR] miner restart err
2025-12-26 17:46:23 [ERROR] ---[S21PT1_CONFIGURE_ASIC_ERR]
2025-12-26 17:46:23 [ERROR] -------[S21PT1_EXECUTE_FREQ_BOOST_ERR]
2025-12-26 17:46:23 [ERROR] -----------[S21PT1_FREQ_UP_ERR]
2025-12-26 17:46:23 [ERROR] ---------------[FREQ_UP_V1_SET_FREQ_STEP_UP_OPERATION_ERR]
2025-12-26 17:46:23 [ERROR] -------------------[S21PT1_VOLTAGE_ADJUST_ERR]
2025-12-26 17:46:23 [ERROR] -----------------------[S21PT1_FREQ_UP_RATE_TOO_LOW_ERR]
2025-12-26 18:11:18 [INFO_] kill all hashboard