Could not launch the profile

A run prints this for one profile when the launch failed and left no reason behind. Every refusal that knows why it happened says so in its own words, so this short line points at the browser being unreachable rather than at a launch being declined.

This line means no reason was given

When a launch has a reason the run shows that reason instead: an account that needs attention, a proxy that is not fully set, a profile written by a newer build.

So the causes below are all about reaching the browser after it started.

The browser did not answer

A run drives the profile through the control channel the browser opens on start, and it waits for that channel to answer before the first step.

Launch the same profile by hand. If the window comes up normally the launch is fine and the connection is what failed.

A second browser holds the folder

One profile folder must never be shared by two browsers, so a second copy of the same profile does not start.

Close the copy that is already open, including one opened on the other engine, and run again.

The window never finished loading

The run gives the first page fifteen seconds. A slow proxy on the start page can spend the whole budget before a single step has run.

No room at this moment

A run does not write a profile off when the open ceiling is reached: it waits for a slot for up to half an hour first.

A failure that arrives instantly is therefore not the ceiling.

One failed profile does not end the run

The rest of the selection is still driven. The report names which profile failed and how many of its steps never ran.

Collecting the evidence

Run the flow again on that one profile so the log stays short, then open the run log: the failed launch is the first line in it.

Write from the Support screen with the flow name and the exact time. The report that travels with the message names the engine and its version.

What this article does not cover

A flow with no steps or with no profiles selected. Those refusals happen before any launch.
A step that failed inside a working browser. The step log names it and the reason is its own.
A flow file that would not import. The importer says what it could not read.

Where this is decided

Each claim above is one place in the code and one stand.

Flows run against the real engine rather than against a stand-in: apps/desktop/test/сценарий-живьём.js
Done means the written steps ran and a failed step is not hidden: apps/desktop/test/run-result-honest.js
A run waits for a free slot instead of writing the profile off: apps/desktop/test/сценарий-ждёт-места.js
A profile already open elsewhere is not opened a second time: apps/desktop/test/profile-busy.js

Questions

Does the run stop at the first profile that fails?: No. It marks that profile failed and keeps driving the rest of the selection.
Is a run with a failed launch reported as done?: No. Done means the steps that were written actually ran, so a profile that never opened makes the run a failure.
Which engine does a run use?: Whichever one the profile launches with. Runs and the synchronizer work on both.

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Still stuck

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