Assuming you have a bought from a reputable trailer supplier and it does habve some form of susopension fitted, yes, the suapension units do go solid over time.
I have an open box trialer that as an experiment I craned 2 tons of bagged gravel on board (thanks to mate with tractor for the help on that one!) Suspension units didnlt move more than about 1/2" between the top of the tyres & the mudguards!
As it's rated for 300Kg nominal, needless to say I am now the proud owner of 2 new suspension units.
What is the trailer rated for? Suspension is one of these things where more isn't necessarily better.........