@MattUK81 

Hello,

For this issue, the ISP update is not necessary, here are some suggestions you can try, thank you!

1. Please confirm with your ISP that the SIM card complies with the Network Type of tp-link mobile wifi device and gets the APN of SIM card. 

Here is the Network Type of M7350, and the SIM card should support this type. 

4G: FDD-LTE B1/B3/B7/B8/B20 (2100/1800/2600/900/800MHz)
3G: DC-HSPA+/HSPA/UMTS B1/B8 (2100/900MHz)
2G: EDGE/GPRS/GSM Quad Band (850/900/1800/1900MHz)

You can also refer to this link to check the Network Type of M7350:

https://www.tp-link.com/en/home-networking/mifi/m7350/#specifications

2. If SIM card supports the network type, please create an APN profile as the instruction below:
https://www.tp-link.com/en/support/faq/794/
Kindly note that the APN information including APN, Username, and password, etc. are provided by your ISP.

If still no Internet, please help us confirm some information:
1. When did you buy the tp-link device and when did the issue start?

2. May I know who is the ISP?  Did you contact confirm SIM card supports the network type with ISP?

3. After creating the APN file, please wait for 5 mins and help us collect the system log:
Advanced -> System Tools -> System Log-> Save Log and send to us

4.  Advanced -> Dial-up -> Dial-up Settings, make a screenshot  and send to us                                

Advanced -> Dial-up -> ISP Update, check the ISP Version and send to us 

May it help and have a nice day!