Troubleshooting sequence previews, snippets, and variables

Last updated: June 18, 2026

When something looks wrong in a sequence preview, a snippet, or a template variable, the cause is usually one of three things: the preview is still rendering, the snippet's data source isn't returning a value, or a template variable is missing and the email is blocked.

"Sequence preview not loading or taking forever"

When you open a sequence and the preview doesn't load (or shows a perpetual loading spinner), the most common causes are:

1. The preview is generating in the background

Sequence previews can take 5–30 seconds to render the first time, especially for sequences with many contacts and complex template variables. Each preview requires resolving every variable (snippets, custom fields, CRM data) for each contact in scope. For sequences targeting hundreds or thousands of contacts, this is non-trivial work.

Wait at least 30 seconds before assuming it's stuck.

2. A missing variable is blocking the preview

If a template variable can't be resolved (e.g., a snippet that requires a contact's job title, and the contact has no job title), the preview may fail to render that contact, and the enrollment moves to Blocked status.

To diagnose:

  • Open the sequence's Enrollments tab and filter by Blocked.

  • Open one of the blocked enrollments to see which variable is failing.

To fix:

  • Populate the missing data on the contact (e.g., add a job title in your CRM).

  • Update the variable's fallback text in the snippet/template.

  • Or remove the variable from the sequence copy if it's not essential.

After fixing the underlying data, blocked enrollments progress on the next evaluation cycle.

3. Browser or session issue

A stuck preview can occasionally be a frontend issue rather than backend:

  • Hard-refresh the browser (Cmd/Ctrl + Shift + R).

  • Clear cache for the Unify domain.

  • Try in an incognito window.

If the preview consistently fails across browsers and contacts, contact support.

"My snippet is defaulting to fallback text when variables are available"

If a snippet is rendering its fallback text instead of the dynamic content you expect, the snippet's data source isn't returning the value you think it should.

Common causes:

1. The field isn't populated for that contact

Even if the field exists on your contact schema, an individual contact may not have a value for it. The snippet sees an empty value and falls back. Check the contact's record to confirm the field has a value.

2. The field name doesn't match

If you're referencing a custom field by name in the snippet, verify the field's exact name in your CRM matches what the snippet expects. Differences in capitalization or punctuation can cause a non-match.

3. The data source isn't returning the data you expect

For snippets backed by an AI agent or external lookup, the source may be returning nothing for that contact (data not available, low confidence, etc.). Open the snippet's logs (if available) to see what was actually returned.

4. Sync delay

If you just populated the field in your CRM, it can take 15–30 minutes for the change to sync to Unify. The snippet renders based on what's in Unify at the moment of rendering.

"Can I use variables in fallback text for snippets?"

Yes. Snippet fallback text supports the same template variables as the main snippet content. This is useful for graceful degradation:

Snippet content: {{Company.Name}} recently raised {{Company.RecentFundingAmount}}. Fallback text: Hi {{Person.FirstName}} — wanted to reach out.

If the primary data isn't available, the fallback uses a less-specific variable (here, the contact's first name) so the email still personalizes rather than falling back to a generic greeting.

Best practice for nested fallbacks:

  1. Most-specific personalization in the main content.

  2. Less-specific personalization in the fallback.

  3. A safe generic phrase as the final fallback if even the second-level variable is empty.

This avoids generic "Hi there" emails when partial data is available.

When to escalate

If you've worked through this guide and the preview, snippet, or variable still isn't behaving:

  • Sequence link.

  • Specific contact ID and the variable/snippet that's failing.

  • A screenshot of the contact's record showing the relevant field value.

Send to support ( 🎫/ @Unify Support) with that context.