Every CODESYS 3.5 Service Pack (SP) changes small behaviors. If a function block is acting weird, the manual might be for SP15, but you are on SP19. The release notes tell you what changed. Download the release notes for your exact version from the same download page as the software. Do not search generic terms like "timer". Search for the exact object name: TON (Timer ON). Do not search "error". Search the exact error code: C0032 or SMC_ERROR .
Here is the honest guide to finding, understanding, and actually using the CODESYS 3.5 manual—without falling asleep. Here is the most common mistake beginners make: they look for one giant PDF called "CODESYS 3.5 Manual." codesys 3.5 manual
It does not exist.