Troubleshooting Leave feedback

This page describes issues you may face while signing documents with GroupDocs.Signature for Python via .NET, and their solutions.

The Python process ends abruptly with “Couldn’t find a valid ICU package” (Linux): the .NET runtime bundled in the wheel cannot start without ICU. Install it (sudo apt-get install -y libicu-dev on Debian and Ubuntu); any ICU version your distribution ships works. Do not set DOTNET_SYSTEM_GLOBALIZATION_INVARIANT=1 to work around it.

“The type initializer for ‘Gdip’ threw an exception”: libgdiplus is missing. Install libgdiplus on Linux or mono-libgdiplus on macOS (brew install mono-libgdiplus). It is needed for:

• stamp signatures and text signatures rendered as an image, in any format;
• barcode, QR code, and image signatures that set a border or transparency;
• every signature on PowerPoint and image (PNG, JPG, WEBP) files;
• text and stamp signature previews.

Text, barcode, QR code, image, and digital signatures on PDF and Office documents work without it.

“Font Times New Roman was not found” or “Font Arial was not found” (Linux): PDF text and digital signatures use these fonts by default. Install the Microsoft core fonts (ttf-mscorefonts-installer) and run fc-cache -f, or set the signature’s font to a font that is installed. Metric-compatible substitutes such as Liberation are not picked up. How to Sign PDFs in a Linux Container covers fonts in depth.

“Package ’ttf-mscorefonts-installer’ has no installation candidate”: the package is not in the default repositories. Enable the contrib component on Debian, or multiverse on Ubuntu (sudo add-apt-repository -y multiverse), and accept the license agreement first. The exact commands are in System Requirements.

“The number of pages cannot exceed 2 in a trial version”: you are running without a license, and the document has more than two pages. Apply a license or set the GROUPDOCS_LIC_PATH environment variable.

Signed pages carry “Created with evaluation version of GroupDocs.Signature”, search reports an evaluation notice instead of a signature’s text, or verification returns is_valid = False for a document that carries the expected signature: these are the other evaluation limits. Apply a license to remove them.

The license is set, but outputs still carry the evaluation line: the license was not applied, and no error tells you so.

• A missing or unreadable file in GROUPDOCS_LIC_PATH does not raise an error, because a license problem must not break the import. Check the path, and in Docker check the volume mount.
• License().set_license(path) raises GroupDocsSignatureException (“License file not found”) only when the file does not exist. A damaged or wrong license file is accepted without an error.

To confirm that a license works, sign a test document and check that no evaluation line appears on its pages. See Evaluation Limitations and Licensing.

is not a supported wheel on this platform or No matching distribution found: check that the system meets the System Requirements:

• Linux needs x86-64 with glibc 2.27 or newer, and macOS needs version 12 or newer.
• pip must be 20.3 or newer to recognize the wheel tags: run python -m pip install --upgrade pip (on Python 3.5, python -m pip install "pip==20.3.4").
• On Windows, use a 64-bit Python: there is no 32-bit wheel.
• On an Intel Mac, a Python built against a pre-11 macOS SDK reports its system as macOS 10.16. Use pip 24.1 or newer, or run SYSTEM_VERSION_COMPAT=0 pip install groupdocs-signature-net.

pip install groupdocs_signature_net-*.whl fails in PowerShell: PowerShell does not expand a * wildcard for a native command. Name the wheel file explicitly.

The mounted license or output path is wrong when running docker run from Git Bash on Windows: Git Bash rewrites container paths. Run export MSYS_NO_PATHCONV=1 before docker run.

See Running in Docker for a complete Dockerfile with every package the library needs.

• System requirements: supported systems, pip, and the Linux and macOS packages (ICU, fontconfig, libgdiplus, Microsoft core fonts).
• Evaluation limitations and licensing: trial limits and every way to apply a license.
• Running in Docker: a minimal image that signs a PDF.
• Technical Support: ask on the forum when your issue is not listed here.