https://forge.codesys.com/forge/talk/Engineering/thread/5e248a0c1b/Recent posts to Codesys Installation problemenTue, 16 Jun 2026 15:24:47 -0000https://forge.codesys.com/forge/talk/Engineering/thread/5e248a0c1b/?limit=25#4924<div class="markdown_content"><p>Hello,<br/> I'm trying to install Codesys SP21p6 (but the error occurs in SP22 too for eg.) but it fails to install ApplicationComposer.<br/> Trying to install myself (version 4.4.0.0 or 4.5.0.0) by clicking 'changing the installation' from the Codesys Installer isn't better.<br/> The only message I get is <br/> "An error occured during the installation: The file <span>[..]</span>/ApplicationComposer.plugin.dll isn't a valid plugin"<br/> How is that? The installation went good the last time before a reinstallation...</p> <p>However, installing the version 4.3.0.0 seems to be successful without knowing what's the difference.</p> <p>I already tried to :<br/> - Restart my computer<br/> - Delete all temporary files in C:\ProgramData\CODESYS\Temporary Files<br/> - Download the package from the store<br/> - Compare the ApplicationComposer.plugin.dll from another computer (where the installation is OK) and it's exatly the same</p> <p>For your information, I can install other packages, such as Codesys CFC</p> <p>Can you help me? Do you have any idea of what could be the problem?</p></div>anthony-pTue, 16 Jun 2026 15:24:47 -0000https://forge.codesys.com52c518c2ceb5cb1f94f697d0d9495f8ead7b8fec