I can half identify with this. I have a lot of friends and make friends easily, but I've always been utterly, utterly invisible to men. I've never been asked on a date, men never approach me, never had a man whistle, leer, catcall me. Been on OLD and apps like Tinder but get hardly any matches and those that do don't message or maybe just message "hi."
I'm not saying I WANT those things (obviously no woman wants to be harassed) but it does feel embarrassingly, like, what's wrong with me? Why do I repel men? In my case it's not due to being middle-aged since I was invisible to men even when I was a teenager/twentysomething and was slim and pretty.
Honestly, I think being able to connect with people (whether romantically, sexually, or platonically) is a knack you pick up when young and if you make it to adulthood without experiencing that, somehow people subconsciously pick up on that. What was your childhood like, how easy or hard did you find it to make friends?
The other part is, it's likely to be at least partly your life/lifestyle. Being on furlough and on lockdown must be very lonely, and it's so tough to keep friendships going when you can't see people in person. I've found that too. I read somewhere the secret to making friends is being in an environment where you're around the same people regularly. I'm really lucky because my job involves constantly meeting new people, but often working with people intensely for several months and it's hard not to make friends under those circumstances. If you're not working (or if your job doesn't involve much face to face contact with others, or you don't get along with co-workers) then opportunities to make friends as an adult are limited, and it's so much harder to make friends when older.
It's a cliche, but are there any hobby groups you can join locally? Like a choir? Just seeing the same people week after week might help you feel more confident?
The other thing I'd say is don't beat yourself up, because Lockdown has really done a number on relationships and friendships.