I'm trying to make a clock pulse generator but when I run the simulation nothing happens
The first important thing that you need to know here is that you are using digital logic gates as analog parts.  You're making them into amplifiers in this case.  This isn't a bad thing, per se, but you're definitely straying off of the applications that the datasheets support.  So you have to dig deep into how the parts really work under the hood.
The second important thing that you need to know is that even when you are using them purely as digital gates, 74HCxx parts are not a direct replacement for 74LS** parts.  You can make it work sometimes, but mixing them gets problematical if you want full speed or glitch resistance, and you definitely can't freely exchange them in an analog circuit.
So -- as Tony Steward pointed out -- you're biasing the parts incorrectly.  In the picture, I've showed the difference.



simulate this circuit &ndash; Schematic created using CircuitLab
Note the wording in the text -- in the case of the 74LS00, I've said &quot;analog range&quot;, where in the case of the 74HC00, I've said &quot;illegal range&quot;.  This is because by the time that the 74HC parts came out, transistors were smaller and cheaper.  The 74LS parts have fewer stages of amplification internally.  They have significantly lower gain than the 74HC parts, which makes them much better behaved than a 74HC when you're misusing them as analog amplifiers.
On the other hand, the 74HC parts have enough gain that they tend to &quot;snap&quot; from off to on -- while they have a gap between their guarantee-high input and their guaranteed-low input, most of this gap in taken up by uncertainty in just where the threshold is, not an area where there's a nice soft transition from &quot;off&quot; to &quot;on&quot;.
This difference is pronounced enough that the 74HCU04 exists -- this is a 74xx04-style inverting buffer, that is intentionally designed to have a better-behaved analog region.  It was introduced by digital designers who knew how to use a 74xx04 to make a crystal oscillator, and didn't want to specify just one 74C04 or 74LS04, or whatever.
So if you do change to the recommended &quot;analog&quot; version of the 74HC00, you may find that the circuit is still poorly behaved.  Where I would expect the 'LS version to settle into a ring oscillator, the 'HC version may end up in a mode where each stage is madly oscillating by itself, against the lead inductance or pin capacitance of the part, rather than going through those electrolytic capacitors as you expect.
If your goal is to just learn stuff -- plow ahead!  If your goal is product design, or to make a reliable hobby project, I strongly suggest that you either use 74LS00 parts as originally intended, or 74C00 parts using my &quot;74HC00&quot; circuit, or better yet, use a circuit based on something intended for the job, like comparators or a 555 timer.