In the More Info section of plant species taxon pages, the link to IPNI + POWO seems to be missing a space or a %20 between the genus and species name. This submits a species name with no space to the search engine which finds nothing. A pretty minor bug which should be easily fixed! Thanks!
Here is an example where the probem occurs: https://www.inaturalist.org/taxa/60284-Elymus-repens