"We can’t process your request." Error on "Add Existing Testers" to Testflight build

Can't add existing testers to build, because error "We can’t process your request. Try reloading the page. If the problem persists, contact us. f7c1a535-feb8-43da-8fd6-3d7da9ddbe12" appears

"We can’t process your request." Error on "Add Existing Testers" to Testflight build
 
 
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