I've had 4 calprotectin results in the past 3 years.
First was around 300, (I had just had covid and some peristent diarrhoea hence the testing of the stool) , it was repeated two weeks later and it was over 2000 - this triggered a colonoscopy but nothing of note was found. I felt absolutely dreadful at the time with loads of digestive symptoms - nausea, lack of appetite, diarrhoea, reflux etc. My tests were on private insurance - I also had a small bowel MRI which was 'normal', so no IBD and no cancer found. So far, so mysterious.
FFwd a couple more months I had another NHS stool test as wasn't feeling any better and had more diahorrea, that was 7 so good, back to normal. My FIT tests have always been normal.
After that I was mainly battling with acid reflux (using diet and gaviscon advance to help, but also was on PPI for a while) and wind but more recently I started getting some more bowel symptoms so the NHS did another round of stool tests and my calprotectin was about 1500 - I've already had colonoscopy, followed by abdo CT - no colitis but they suspect chrons as there was inflammation and a enlarged node. Having a small bowel CT with contrast and another endoscopy in the next few days, which will hopefully give the answers.
So the upshot is I have some mild inflammation in the bowels, but they can't determine what is causing it. I did have h pylori which was treated, but I do wonder if that is the culprit and it didn't get eradicated. Although on googling it says h pylori doesn't raise calprotectin levels.
So my answer is, get tested but you may end up going down a testing rabbit hole.
90 isn't particularly high for calprotectin though, and you have to be eating wheat to be tested accurately for coeliac.