AVR microcontroller cannot enter programming mode

The AVR microcontroller ATmega16 was used in the project. The editing and compiling environment during the learning process was ICCAVR, and the parallel port downloader and PonyProg2000 software were used to download the program. When the project was almost done, considering that if I wanted to debug the program on site and still use the parallel port downloader, I would have to bring a desktop computer or buy an EXPRESSCARD, which would be very inconvenient, so I considered using a laptop. Later, I bought an AVR two-in-one tool from Shenzhen Yanxue Electronics Co., Ltd. After installing the USB driver and AVR Studio software according to the CD information, connect the AVR two-in-one tool to the computer USB port and the target board, open the AVR Studio software, click the button on the toolbar, and the following dialog box will appear:

Click the Connect button and the following dialog box appears:

Then click the Program button in the Flash group and the following dialog box will appear:

We can see that Entering programming mode.. FALILED! is displayed in the history operation window, which indicates that we have failed to enter the programming mode.

Then I searched the Internet to find out the reason and see if there were any friends who had the same problem as me. But the posts I saw only asked questions, but no one solved the problem. Then I searched the website of Shenzhen Yanxue Electronics Co., Ltd.! I found a very crucial sentence, haha.

The download line needs to operate the reset pin to achieve synchronization, so when designing the target board, do not make an external reset and watchdog circuit. The AVR already has a hardware watchdog, so a pull-up resistor is enough.

Then I removed the reset capacitor and the problem was solved. Later I found that replacing the reset capacitor with 100uf/16V would not cause the above problem.