Unsupported MIME Type on a ForNAV Report Layout
The ForNAV Health Check might report an Unsupported MIME type result for one or more report layouts. This article explains why this issue occurs and how to resolve it permanently.
Note: In versions 8.2.x.2 and earlier, the report might not work at all when this problem is present. The report preview does not generate any output.
Why this error occurs
FORNAV layouts that use the External layout type must have their MIME type set to FORNAV. When the MIME type is set to any other value, the layout cannot be processed correctly.
The most common cause is the Report Layouts page in Business Central. When a user opens that page and inserts a layout record, Business Central sets the MIME type to a default value. This overwrites the FORNAV MIME type that FORNAV requires.
Impact
FORNAV detects the incorrect MIME type at runtime and ignores the issue instead of raising a hard error, so your reports continue to run. However, the layout might not work properly or it might stop functioning after a future upgrade.
How to resolve the issue
Option 1 — Use the Health Check Auto Fix (recommended)
Note: Version 8.2.x.3 or later is required to use the auto fix for this issue.
- Open the ForNAV Health Check page.
- Run a health check. Layouts with an unsupported MIME type are listed with the result Unsupported MIME type.
- Select the affected line and click Auto Fix.
The Auto Fix action corrects the MIME type on the layout record so that it is set back to FORNAV. This is a permanent fix.
Option 2 — Edit the layout with the FORNAV Designer
- Open the FORNAV Reports page in Business Central.
- Locate the report, open the card and locate the layout (the layout name is shown in the health check error message).
- Select the layout and click Design. This will open the layout in the FORNAV Designer.
- Select either Save as custom layout or Save as custom layout and activate.
Preventing the issue
Avoid importing layout records directly on the Report Layouts page unless necessary. Use the FORNAV Designer or the FORNAV-specific layout management pages to manage FORNAV layouts. These pages preserve the FORNAV MIME type correctly.
Related Health Check results
| Result | Description |
|---|---|
| Unsupported MIME type | The layout has an External layout type but the MIME type is not FORNAV. |
| Layout not converted to FORNAV | The layout is still using the old Word layout type and needs to be converted. |
| Report not converted to FORNAV | The report extension has not been converted to use External layouts. |
For more information about converting layouts to the External layout type, see the FORNAV knowledge base article on layout type conversion.