---
title: "Common issues"
description: "Fix the issues that stop a flow from previewing, publishing, or behaving the way you built it in the Flow Builder."
---

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This article collects the issues that come up most often while building a flow in the [Flow Builder](adapty-flow-builder), each with its cause and its fix.

## A flow won't preview or publish

You can't publish or preview your flow if any of the following issues are present.

- An interaction with an incomplete configuration. Common cases:
    - An **Open URL** action without a target URL.
    - A **Navigate to screen** action without a destination — also occurs when the destination screen is deleted after the action is set up.
    - A **conditional action** without an operator or value.
    - A **Set variable** action without a variable/value assignment.
    - A **Purchase** action with no product (in-app store) or no Web Paywall URL (web payment).
    - A **Custom** action without an Action ID.
    - A **Show alert** action with an empty Title or Message.
    - A **Show** or **Hide** action with no element selected.
    - A **Select product** action with no target product — also occurs when the target product element is deleted, moved out of its product group, or left on another screen.
    - A **Select product** action saved inside a reusable component, or one that targets an element ID used on more than one screen.
- A **screen with no elements**.
- A product element **without a product attached** — may occur if you remove the referenced product.
- An invalid **remote config** JSON breaks the entire delivery process — you cannot even save the draft.

To catch these before publishing, [preview the flow in the Adapty app](paywall-device-compatibility-preview). If the flow fails to load there, the error message gives you more detail.

## A Set variable action doesn't change the selected product

Which product is selected isn't a variable you can assign, so **Set variable** can't move the selection. Use the [**Select product**](onboarding-actions#select-product) action instead.

## An image or video won't upload

A file outside the Flow Builder's media limits won't upload. Verify the file against the [Image](custom-media#image) and [Video](custom-media#video) requirements:

| Element | Formats | Maximum file size | Other limits |
| :--- | :--- | :--- | :--- |
| Image | `.JPG`, `.PNG`, `.WEBP` | 20 MB | — |
| Video | `.MP4`, `.WEBM` | 50 MB | 30 seconds maximum; 640×640 pixels minimum |

These formats aren't supported:

- **Animated GIFs and animated WEBPs**: To add motion, use a Video element instead.
- **SVG**: Export the file as PNG or WEBP. For icons, you don't upload anything — the Icon element draws from the bundled [Tabler Icons](custom-media#icon) library.