Sorry for long post, and may not be just for the OP, but this topic can make or break some trainees into being somewhat lost for long periods of time, or knowing how to go with the flow of the waves in training and adaptation and compensation of the body's system(s).
Plateaus, are actually a common part of training, (especially as one gets more and more into training or advanced) you are not really built to grow in a linear fashion. (Everything in nature waves or rests and pulses) Just because one stops on what they may think is a very visual or progressive upgrade, does not mean they quit progressing on actually building the body to adapt to higher levels.
It does take some experience and understanding to learn the slow processes of the body, so patience can be a virtue here too.
If you are gaining strength in any part of the body ie: many times the legs or lower body or pos chain, will take a long time to show up, before say smaller groups such as arm curling strength. This does not necessarily mean a plateau, as much as it may be the body trying to balance itself out more or catch other areas up to some degree.
There are lots of ways or things to add or adjust, to get what can be a bump, (tweaks in routines, focus in specific groups, more cals as was mentioned, deloads, maybe less intensity, maybe more intensity, maybe more volume, less volume, more frequency, less frequency, maybe nothing really needs to change at present, but to stay the course, it can go on and on.
I think one of the important things to remember (especially if you are fairly new to training) is that, it is probably better not to jump in to changing a bunch of things at once, or constantly hunting new routines, in search of a quick fix. Might be better to change "one" thing and then go for a while. I have had weeks/maybe months where I just did not seem to add anything and even have to drop weight from the bar, only to come back a few weeks even months later, and hit a PR. Your body cycles like that.
Your body adapts slowly and over periods of time.
Being consistent and learning to pay close attention to small things, will most likely serve you best and grow your body along with your wisdom in training and gaining for many years.
Not at all implying novices or even intermediates have to get this deep in theory, but as one advances, you may have to learn that progress does not come weekly or even monthly, even though you are sticking the routine and drilling it week after week, building say a larger base, or improving mental skills and or work habits. Anyone who has trained for a while and learns their body, knows this.
Training theory, can get and be quite advanced. And learning how to manage it, can be key to being either a champion or armchair athlete.