A package isn't found, the XAML Designer asks to restart, code in the constructor has no effect or the application fails on the machine of a user. What you see usually tells you where to look, and each page of Troubleshooting starts from such a symptom, quotes the message where TX Text Control shows one, explains the cause and gives the steps that fix it.

Find the Right Page

If you see	Read
A package isn't found, doesn't install or doesn't fit the target framework	Installation and Package Restore
The XAML Designer asks to restart, the toolbox tab is missing, or the bars aren't connected	Toolbox and XAML Designer
XAML doesn't recognize the controls, or the project references old assemblies	XAML Namespaces and Assembly References
Code in the constructor of the window has no effect or fails	Control Initialization
A binding to the formatting doesn't update, or a property can't be a binding target	Data Binding and Commands
The window freezes while documents are processed, or an exception ends the application	Dispatcher and Thread Access
"The following control could not be licensed", an expired trial or a `LicenseLevelException`	Licensing
"The TX Text Control kernel DLL file could not be found", or the application fails when the engine starts	Native Libraries and Architecture Mismatches
Text in another font, moved line and page breaks, or a PDF/A document that can't be saved	Fonts and Document Layout
Blurry icons of your own buttons, or a zoom factor that isn't applied	DPI and Scaling
Printing is disabled, ignores the print dialog or looks different from the screen	Printing
A `FilterException`, or a loaded or converted document that looks wrong	Document Conversion
Merge fields or blocks that stay empty or disappear	Mail Merge
An application that runs on your machine but not on the machine of a user	Deployment

Collect the Evidence First

Most problems are quicker to solve with the right information at hand:

The version and edition. GetVersionInfo returns the product level and the service pack the application runs with. See Check Which Edition Your Application Runs.
The reason of an exception. A FilterException names its cause in its Reason property and an error number in its message. See Read the Reason of a FilterException.
The replaced fonts. The AdaptFont event reports every font that isn't available. See Find Out Which Fonts Are Replaced.
When your code runs. Code that runs before the Loaded event of the TextControl finds a control that isn't ready. See Control Initialization.

Check the Known Issues

Text Control keeps a list of known issues for each major version, on the page Known Issues of TX Text Control .NET for WPF 34.0. It names each issue with its ID and area, groups the closed issues by the service pack that fixed them, and lists the issues that are still open. The service pack announcements on the blog link the same page.

Read the service pack your application runs with, as Check Which Edition Your Application Runs and Service Packs show.
Look for your problem on the page. If a later service pack fixed it, install that service pack, update the package and rebuild the application.
If the issue is open, it isn't fixed yet in any service pack of the version.

For an earlier major version, replace 3400 in the address with its number, such as 3300 for version 33.0.

Contact Text Control Support

When neither these pages nor the known issues solve the problem, contact Text Control through the contact page. A subscription includes technical support by email, telephone and chat, with no limit on the number of incidents; see Subscription and Updates. Send the evidence listed above with your request: the version, the edition, the service pack and the complete message with its error number.

Where to Start

A new project doesn't build or run: start with Installation and Package Restore, then Toolbox and XAML Designer, XAML Namespaces and Assembly References and Licensing.
The editor doesn't behave as expected: Control Initialization first, then Data Binding and Commands.
The application fails on another machine: Deployment first, then Native Libraries and Architecture Mismatches.
Documents look wrong: Fonts and Document Layout first, then Document Conversion.
Nothing on these pages matches: check the known issues of your version.

If a problem started after an update, check the Breaking Changes of the versions you skipped. The Deployment Guide shows complete setups that avoid many of these problems.