no cortex-m device found in the jtag chain. please check the jtag cable and the connected device

hello everyone
i am working on stm32h103 board and i load the programs with KEIL.when i was programming , the KEIL returns to me "no cortex-m device found in the jtag chain.
please check the jtag cable and the connected device"
and in the message box , it returns to me
"JLink Info: Could not measure total IR len. TDO is constant high.
**JLink Warning: No matching core found. Selecting default core (ARM7).
* JLink Info: Could not measure total IR len. TDO is constant high.
***JLink Error: Could not find supported CPU core on JTAG chain"
please help to find the trouble.

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