If you get the prompt, and your character initiates the action, then abruptly stops, you are too close to the structure, and you need to try to move back farther before you can build the shelter. If you do not get the prompt to build the shelter, it is likely that it is being shielded by another hit box around your build site, take care to try it from multiple angles. Generally, if the shelter can be placed, it can be built. In some cases, inside some buildings you are able to place the kit closer to the walls than you can actually build the shelter. You may need to move the shelter to a different location.

Hello.
As the user commented above. Can you please try to stand further from the shelter when creating it? Player collission might prevent the structure from being built.