Still a problem this morning. As a test, while iSpot was failing to upload one photo with egg-timer spinning endlessly, I opened another browser window and uploaded the same photo and two others to FaceBook without any problem.
i wonder how it would go if you opened a second iSpot in another Window and tried there?
If it goes well, it MIGHT suggest you have a rouge setting
Whilst I have hold ups, I rarely fail to get a photo up nowadays.
I just get two spinning egg-timers in different windows 
As things stand, the site is unworkable for me.
Are you able to share some of the images that are being rejected to me via something like Dropbox? Iād like to try uploading them myself - via different browsers too.
I could but this seems to be exactly the same problem I encountered a week or two ago. At that time you had no difficulty uploading some photos I sent you, nor did Derek. Given that other sites (eg FaceBook, DropBox) manage to receive images from me, I find Iām pointed strongly to believing that itās a problem between me and iSpot (and even iSpot seems to manage sometimes.) Trying other images, deleting iSpot cookies and trying other browsers doesnāt seem to make a difference.
iSpot makes use of JavaScript code called Angular for its front end and makes the browser do a certain amount of work in the image upload process. When we were updating the code, we really struggled with image upload and sometimes it turned out to be a permissions issue - the browser seemed to think it was logged out of the site even though if you looked at the home page it didnāt show the login box. This is why I suggested clearing the cookies for our domain.
The upload process also causes the browser to use a lot of memory so if you have a lot of browser tabs or windows open, that can affect things.
I cannot get onto the site at all using Firefox at the moment. But itās working fine in MS Edge (which I donāt normally use). Itās frustrating as Iād spent a fair while uploading an observation on firefox and then when I pressed āconfirmā, it just said: āObservation not uploadedā and I couldnāt even get back onto the site after that.
having written the above, and getting messages saying āSomething has gone terribly wrong, clear you cookies and browser cacheā on Firefox; an hour later and it is all working swimmingly - and I havenāt cleared anything 
In 3 different browsers (Chrome, Edge, Firefox) Iāve just tried deleting site cookies, logging in and trying to post an observation. Just 1 window in each browser. No other applications running. In each of them I get
with only some differences in the length of the progress bar. Same result with Chrome on a different computer.
Could it be that something has been done fairly recently which gives problems with Windows 10 (which Iām using on both machines)?
All I can suggest is sending me the images so I can try an upload myself.
Chris, do you still have the Bramble Rust (Phragmidium) photos I sent you a couple of weeks ago? Iāve just tried, and failed, to upload one of those. Do they still work OK for you?
Yes I do - in fact Iāve been doing a lot of testing with them. Iāll try some uploading on the live site nowā¦
Just tried one, then two then the rest - and they all - eventually - completed their uploads. So iSpot itself appears ok at the moment.
Managed to post https://www.ispotnature.org/communities/uk-and-ireland/view/observation/869231/entomophthora-sp-on-tipula with a cropped photo after several (8-10?) failed attempts with both the full-size and cropped photo.
This problem - of photos hanging up, has been with me for a long, long time time. I overcome it, usually, by adding the same photo to the queue. In a few cases, I just abandon the task
this is on a Saturday10am. The Broadband speed is normal, iSpot is running quite well
It seems to have been OK me for for a day or two, without any changes at my end AFAIK. Iāve just uploaded a batch of 9 images, a total of 22.4MB, and they went without a hitch: see https://www.ispotnature.org/communities/uk-and-ireland/view/observation/869805/alder-tongue-taphrina-alni