The clue is in the error message (this is knowledge you'll gain over time).
errTmActiveLockConflict means the TiVo is busy doing something else. You have to keep in mind that TiVoweb is a massive hack and the TiVo wasn't designed to be nice to alien code running on it! Sometimes tivoweb doesn't get a look-in, can get stuck. Sometimes quiting and restarting Tivoweb does the trick, but sometimes you have to reboot the TiVo.
In general with TiVoweb, you need to retry a few minutes later. If it doesn't work, quit and restart TiVoweb. If it doesn't work reboot. If it still doesn't work, it might be a problem with the code.
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NB: on a clean TiVo with no Season Passes (created with the UI) or guide data you will always have problems with TiVoweb. It needs to make a call and fill up with data, and have 1 season pass, 1 to-do item and 1 now playing item before it'll be happy.
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links to my TiVo logos, TivoWebPlus 2.1.b3 UK-20120818, Tracker v3.3.3 & v3.3.4 (17th Jun 2013), GDchecker v1.06b, Digiguide checker v0.4.3-rc5 and Autospace v1.65 can all be found in
this post.