No channels for imported forms

I did the following:
1. Installed CF7 and Flamingo
2. Set up reCaptcha integration
3. Imported several CF7 forms through Tools->Import->WordPress Importer
4. Made a test page with the shortcode of an imported form

All is working fine except that in Flamingo there are no any channels for the submissions: the column “Channel” is empty and the drop-down list of the channels is absent.

When I use the preinstalled form named “Contact form 1”, the submissions are marked “Contact Form 7 / Contact form 1” and the drop-down list of the channels appears.

How to make channels appear for the imported forms?

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