Where has all the jelly gone?

Four years ago, the jelly lichen on the rough part of the back patio was clearly doing very well, as shown at reference 1. More recently it has been doing badly, and I am not sure if it appeared at all last year. This year there is a sprinkle. Is it going to grow in the weeks to come? Why has it gone missing for a year or more?

PS: quite a lot of the bits of dead oak twig which fall onto our back garden have blobs of spongy looking black stuff on them. Maybe these are jelly lichens too and I clearly need to take a proper look. Which prompts a need for the sort of pocket microscope which my elder brother often used to carry about. The size and shape of a large fountain pen and very handy for looking at stuff in the field. Can Amazon oblige? Answer yes, with plenty of them less than £20. But the only one that looks like a fountain pen comes in at £80... Perhaps a spot of advice is in order.

References

Reference 1: https://psmv3.blogspot.com/2018/03/old-phone-two.html. A good year for jelly lichen.

Reference 2: https://en.wikipedia.org/wiki/Collema. A list of the jelly lichens.

Reference 3: https://www.britishlichensociety.org.uk/. 'A lichen is not a single organism; it is a stable symbiotic association between a fungus and algae and/or cyanobacteria. Like all fungi, lichen fungi require carbon as a food source; this is provided by their symbiotic algae and/or cyanobacteria, that are photosynthetic. The lichen symbiosis is thought to be a mutualism, since both the fungi and the photosynthetic partners, called photobionts, benefit'. Lots of good stuff here about lichens in general, but not all that much on jelly lichens in particular.