I'm using Android phone, no issues on my end.
What phone model are you using?

Probably not helpful but, have you tried restart your phone?
As what I know, Ultra Box didn't specifically mention any support of WPA3, and I don't set my home WiFi network as "WPA3 only", so I'm not able to comment on that.
Any major concerns if you'd configure your route's WiFi network as mixed WPA2/WPA3 mode?

Previously was using a Lan cable but it seems to have damaged.
Perhaps, have you try look around your house for LAN cable, especially those LAN cable included from the box packaging of your older/previous WiFi-related devices and routers.
Otherwise, why not buy new one? It's not expensive anyway.

For me, my WiFi router supports WiFi 6, and the network is on mixed WPA2/WPA3 encryption (there's no option for WPA3 only in the settings), and my Ultra Box still able to connect the WiFi network without issues, so I think the issue you're facing is probably something else?

Have you made sure that your WiFi frequency channel is not heavily interfered/clashed by your neighbour's WiFi network's frequency channel?
What other settings did you change on your router? MAC address filter? DHCP settings? You tried reboot both the WiFi router and your Ultra Box as well, right?

You mentioned that you're using TP-Link Archer A53 router, and you face this issue... I assume you changed new router, is it?
Then how about your previous WiFi router? All along working fine?
Are you not able to connect both 2.4GHz and 5GHz from your WiFi router, or which either one?

Previously how did you get your Ultra Box connected to the Internet? Since the user manual of your Ultra Box stated that the Ethernet port is only 10/100Mbps, then why not just use back your existing LAN cable? I don't think there's a need to buy a CAT7 cable for that.

If you've exhausted all steps and issue persists, you can try perform clear NVRAM on your Ultra Box as a last resort.
So many ways to troubleshoot, you figure out one by one la.

I’m on the basic pack (RM70+) and I don’t qualify for the free ultra box upgrade but I’m willing to pay extra for the ultra box since you told me it’s more stable.

Regardless if you subscribe Astro Fibre right now or after your current contract ends, you will still get a fresh new 24 months contract for your Astro subscription, and it starts from the day of installation.

If subscribe to apps (i.e. Netflix), then you'll see something like 'Reverse charges' on the bill. Prorated charges will start from the day you subscribe until your billing date. 
If remove apps (i.e. Netflix), then no proration at all.

Hi joshhd,

Current pack is Namma Pack+Sports Pack and Multi room. When I called earlier in Aug, there was once they offered RM120+ with tax with no contract but I could not confirm but subsequently when I called in Sept no such offer was made. I'm not sure if I'm asking for the right options. I called 03-95433838. They instead ask to cancel multi room which not an option for the 2 elderly folks that need both decoders to ensure a peaceful time of not arguing which channel to watch .

Any advise would be great as it's too much to pay for limited use.

I think the poster is from the sale agent, not directly from Astro. There's no announcement of Deepavali promotion on its official website. Only countdown to 10 10 sale.

LOL.
Since Deepavali is around the corner, hence sales agents would do this to create the hype to target Indians, as this could potentially produce more sales. 

From what I see, keywords like "Deepavali Promotion 10 days only" creates a sense of urgency and to attract your attention, especially towards potential new customers. If more customers signs up during this "Deepavali week", then it'll look good on either that sale agent's KPI, or that sale agent's team KPI, or both. Also, more commission too.

Now that you posted this thing here, it means they've successfully captured your attention. So, good job to the sales agent?
Actually, it's just their ongoing Astro One: Entertainment Pack RM49.99 offering, with the same installation fee and so on.

And even so, it's meant to target new sign ups, not for existing customers to see.
For existing customers like all of us here, Astro would rather want you to "stay where you are" than switching to Astro One packs.

EDIT: Also, that guy on the poster looks like AI-generated rather than an actual person 🤭