Table of contents
1. The download page on the mobile phone cannot be opened.
Solution 1) Computer side - set the network to public (valid for personal testing)
Solution 2) Set fiddler as a trusted application on the mobile phone so that it will not be intercepted (not tried yet)
2. This certificate cannot be installed
Method 1: Change the certificate suffix cer to crt (unsuccessful)
Method 2: Change the browser on the mobile phone and turn off the firewall on the computer (successful)
3. After setting up a WiFi proxy, the network connection is limited.
4. Some APPs can capture packets, but some cannot (unsolved)
1. The download page on the mobile phone cannot be opened.
Possible Causes:
1) Computer: Computer devices cannot be discovered by mobile phones
2) Mobile version: fiddler is intercepted by the firewall
Solution 1) Computer side - set the network to public (valid for personal testing)
Solution 2) Set fiddler as a trusted application on the mobile phone so that it will not be intercepted (not tried yet)
What to do if fiddler cannot open the certificate download page when connecting to the mobile phone's IP+port. _Chasing Light's Blog - CSDN Blog_The fiddler certificate download address cannot be opened. There are many tutorials on how to connect fiddler to a mobile phone on the Internet, so I won't go into details here. The main explanation is that the certificate download cannot be opened when accessing the IP+ port on the mobile phone. How to deal with pages. 1. Check the IP when manually configuring the phone: IPV4 address as shown in the figure 2. Check whether the firewall (1): Allow applications to pass through the firewall has been checked to allow fiddler to pass through the firewall. If not, please add fiddler to allow it to pass through the firewall. If so, If fiddler is not found in the list, please click Change Settings and click again to allow other applications to find the installation location of fiddler to add fiddler (2): Simple and crude method: turn off the firewall.. 
https://blog.csdn.net/weixin_44782176/article/ details/119083683
2. This certificate cannot be installed
Method 1: Change the certificate suffix cer to crt (unsuccessful)
[Problem Record] When fiddler installs the https certificate, it reports an error "The certificate cannot be installed because the certificate file cannot be read."_The blog of a tester in the IT world - CSDN blog_The certificate cannot be installed because the certificate file cannot be read. Problem: Fiddler installs the https certificate The error "The certificate cannot be installed because the certificate file cannot be read" Setp1: Download the certificate Setp2: Install the certificate. Error: The certificate cannot be installed because the certificate file cannot be read. Try to solve 1. Crazy Baidu, all the answers found are the following answers 2. According to the Baidu operation results, the same error message cannot be installed because the certificate file cannot be read. 3. Use the emulator to install the certificate. Following the same steps, the installation was successful. Look at it for a long time. It was found that the suffix name of the downloaded certificate was different from that of the simulator. The suffix of the certificate downloaded on the mobile phone is .cer, and the suffix of the certificate downloaded by the emulator is .crt4. Try to manually modify the certificate suffix in the mobile phone, modify and model https://blog.csdn.net/z_erduo/article/details/123835215
Method 2: Change the browser on the mobile phone and turn off the firewall on the computer (successful)
1) Use a third-party browser to download the certificate;
2) Search [Install Certificate] from Settings>>>>Certificate to install;
3) Turn off the firewall on the computer
Here, after entering Toutiao, you can see that the captured image is the same as the image on the mobile phone.
3. After setting up a WiFi proxy, the network connection is limited.
Delete WiFi, reconnect and enter password to solve the problem
4. Some APPs can capture packets, but some cannot (unsolved)