I have experienced similar problems since the beginning of the year. After a Windows update at the end of last week, indexing failed again and I had to go back to rebuild once again. This time it completed at around 148,000 items, whereas a previous rebuild finished around 290,000 items. Once again, I found that the search function in Outlook would not provide results other than for about a handfull of recent emails. In other words, a totally useless exercise. So once again, I went through the rebuild process. It got to 47,361 items then stalled today. Nothing I tried would get it to re-start. I found a post above which directions on how to restart Indexing, with a slightly different route, because some of the steps listed on my Windows 11 machine did not exist. I went to Control Panel> Windows Tools> Services> right click on Windows Search and click re-start. But nothing happened. I then tried right click on Windows Search, click on stop and then click on start. This time indexing resumed its indexing. I will wait and see what happens now, but it will likely take another two days to complete, if at all. Just checked again and indexing is continuing nicely.